WO2022000031A1

WO2022000031A1 - Novel compounds

Info

Publication number: WO2022000031A1
Application number: PCT/AU2021/050691
Authority: WO
Inventors: Jun Zeng; Mehrdad NIKFARJAM; Hong He
Original assignee: Pakinax Pty Ltd
Priority date: 2020-06-30
Filing date: 2021-06-30
Publication date: 2022-01-06
Also published as: US20230242519A1; AU2021302681A1

Abstract

Described herein are compounds that are inhibitors of p21-activated kinases (PAKS). In particular, the compounds described herein are demonstrated to be selective PAK4 inhibitors. The compounds described herein are also demonstrated to reduce the expression of key immune checkpoint molecules, such as PD-1 and CHEK2. Also described herein are pharmaceutical compositions containing such compounds, methods for using such compounds in the treatment of cancers, more specifically, the treatment of pancreatic and lung cancers, and to related uses.

Description

NOVEL COMPOUNDS

Field

The present disclosure relates to compounds that are inhibitors of p21 -activated kinases (PAKs). The disclosure also relates to pharmaceutical compositions containing such com- pounds, methods for using such compounds in the treatment of cancers, more specifically, the treatment of pancreatic and lung cancers, and to related uses.

Background

Cancer is the term given to a collection of related diseases in which abnormal cells divide in an uncontrolled manner, such that they invade nearby tissues. Cancer is recognised as a leading cause of death, with the Agency for Research on Cancer estimating 18.1 million new cancer cases, and 9.6 million cancer deaths, in 2018.

The p21 -activated kinases (PAKs) are a family of serine/threonine protein kinases with two subgroups: PAK1, PAK2, and PAK3 (subgroup I), and PAK4, PAKS, and PAK6 (subgroup II). Since their discovery in the mid-1990s, the understanding of the regulation and biology of these important signalling proteins has increased tremendously, with the PAKs thought to play a role in cytoskeletal organisation, cellular morphogenesis, and cell survival. As a consequence, the PAKs have been implicated in many diseases, including cancer, infectious diseases, and neurological disorders.

In particular, it is PAKs recognition as being integral to growth factor signalling net- works, as well as oncogenic processes that control cell proliferation, cell polarity, invasion and actin cytoskeleton organisation, that implicates them in major, yet varied, roles in the oncogenic processes. To date, a number of cancers have been associated with alterations in the expression and/or activation of PAKs.

Of the PAK family, the PAK4 sub-type is a key downstream effector of the RHO family of GTPases downstream of Ras (Dart and Wells, 2013), and is found to be particularly over- expressed in pancreatic ductal adenocarcinoma (PD AC) cells compared to normal human pan- creatic ductal epithelia (Hakoshima, Shimizu, Maesaki, 2003; Himmelman, Hezel et al, 2008; Mahlamaki, Kauraniemi et al, 2004). As a consequence, PAK4 is an attractive therapeutic target in cancers, particularly PD AC cancer, pancreatic cancer, colon cancer, prostate cancer, and lung cancer.

The inhibition ofPAKs therefore presents as a useful therapeutic target in the prevention and/or treatment of cancers, and other disorders. However, few PAK inhibitors with satisfactory kinase selectivity and drug-like proper- ties have been reported to date. There are even fewer reported potent PAK inhibitors that are selective for particular PAK sub-types, including PAK4. There is therefore a need for novel, potent, and/or selective PAK inhibitors.

An emerging field of cancer therapeutics are the immunotherapies. Immunotherapy re- fers to the treatment of a disease by activating or suppressing the immune system. The T cells of the immune system possess the capacity to selectively recognise and kill pathogens or un- healthy cells, including cancer cells, by orchestrating a coordinated immune response. Many checkpoints ensure that the cells of the immune system do not mistakenly destroy healthy cells during an immune response (known as an autoimmune reaction). Cancer cells can exploit these immune checkpoints as a way to evade immune detection and elimination.

There are numerous immune checkpoint molecules that may provide a target in cancer therapy, including, but not limited to, A2AR, BTLA, CTLA-4, NOX2, TIM-3, and LAG3. To date, these inhibitory checkpoint molecules remain relatively unexplored in cancer therapy.

One such immune checkpoint molecule, the programmed cell death- 1 (PD-1) receptor, is expressed on the surface of activated T cells. Its ligands, PD-L1 and PD-L2, are commonly expressed on the surface of dendritic cells or macrophages. PD-1 and PD-L1/PD-L2 belong to the family of immune checkpoint proteins that act as co-inhibitory factors that can halt or limit the development of the T cell response. The PD-1/PD-L1 interaction ensures that the immune system is activated only at the appropriate time in order to minimise the possibility of chronic autoimmune inflammation.

PD-L1 is commonly over-expressed on tumor cells or on non-transformed cells in the tumor microenvironment. PD-L1 expressed on the tumor cells binds to PD-1 receptors on the activated T cells, which leads to the inhibition of the cytotoxic T cells. These deactivated T cells remain inhibited in the tumor microenvironment. Accordingly, by blocking immune checkpoint proteins, including PD-1 and PD-L1, it has been found that the immune system can overcome cancer’s ability to resist the immune responses and stimulate the body’s own mech- anisms to remain effective in its defense against cancer.

Examples of approved cancer therapies which act via blocking the interaction between PD-1 and PD-L1 include the antibody products Keytruda^® (pembrolizumab) and Opdivo^® (nivolumab).

While immune checkpoint inhibition through PD-1 blockade has brought significant treatment benefits, the currently approved agents have limitations, and the potential for devel- opment of resistance may be a major obstacle to long-term treatment with those agents. Accordingly, there remains a need for new therapies for treating cancer.

Summary

The subject matter of the present disclosure is predicated in part on the surprising dis- covery that compounds of Formula (I) are inhibitors of PAK and have antiproliferative effects. The examples also support that the compounds decrease expression of the immune checkpoint molecules, PD-L1 and CHEK2, and so find application in immunotherapy.

The compounds described herein are PAK4 inhibitors, and are also considered to be molecules that may modulate the tumour microenvironment to enhance the efficacy of immune checkpoint inhibitors, and may bring significant improvement to the immune checkpoint block- ade when used in combination therapy.

Accordingly, in one aspect there is provided a compound of Formula (I) or a salt thereof:

Formula (I); wherein R¹, R³, and R⁵ are each independently selected from the group consisting of hydrogen, halogen, -C_1-6alkyl, -O-C_1-6alkyl, -C_1-6haloalkyl, -O-C_1-6haloalkyl, -C_2-6alkenyl, -C_2-6alkynyl, C_3-10carbocyclyl, 3-10 membered heterocyclyl, -CN, -OR¹¹, -SR¹¹, -NR¹¹R¹², -COR¹¹, -CO₂R¹¹, -CONR¹¹R¹², -NR¹¹COR¹², -SO₂R¹¹, -SO₂NR¹¹R¹², and -NR¹¹SO₂R¹², wherein said alkyl, alkenyl, alkynyl, carbocyclyl or heterocyclyl may be unsubstituted or substituted with one or more substituents each independently selected from the group consisting of halogen, C_1-4alkyl, 0-C_1-4alkyl, C_1-4haloalkyl, -O-C_1-4haloalkyl, -CN, - OR¹¹, -SR¹¹, -NR¹¹R¹², -COR¹¹, -CO₂R¹¹, -CONR¹¹R¹², -NR¹¹COR¹², -SO₂R¹¹, - SO₂NR¹¹R¹², and -NR¹¹SO₂R¹²;

R² and R⁴ are each independently selected from the group consisting of hydrogen, halogen, — C_1-4alkyl, -O-C_1-4alkyl, -C_1-4haloalkyl, and -O-C_1-4haloalkyl; n is an integer of from 0 to 2;

X is S, O. orNH;

R⁶ is selected from the group consisting of hydrogen, halogen, -C_1-4alkyl, -O-C_1-4alkyl, -C_1-4haloalkyl, and -O-C_1-4haloalkyl;

R⁷ is selected from the group consisting of hydrogen, halogen, -CN, -C_1-6alkyl, -C_3-10carbocy- clyl, -C_3-10heterocyclyl, -O-C_1-6alkyl, -O-C_3-10carbocyclyl, -O-(3-10 membered heterocyclyl), - NH(C_1-6alkyl), -N(C_1-6alkyl)₂, -NH-C_3-10carbocyclyl, -N(C_1-4alkyl)-C_6-10carbocyclyl, -NH-(3- 10 membered heterocyclyl), -N(C_1-4alkyl)-(3- 10 membered heterocyclyl), -C(O)-C_1-4alkyl, - C(O)-C_3-10carbocyclyl, -C(O)-(3-10 membered heterocyclyl), and -C(O)N(C_1-4alkyl)₂, wherein said alkyl, carbocyclyl or heterocyclyl may be unsubstituted or substituted with up to two substituents each independently selected from the group consisting of -C_1- ₄alkyl, oxo, halogen, and -C_1-4haloalkyl;

R⁸ is selected from the group consisting of hydrogen, -C_1-8alkyl, -O-C_1-8alkyl, -C_1-4alkylene- R¹³, -O-C_1-4alkylene-R¹³, and -OR¹³;

R⁹ is selected from the group consisting of hydrogen and halogen;

R¹⁰ is selected from the group consisting of hydrogen, -C_1-6alkyl, -C_1-6haloalkyl, -C_6-10aryl, - R¹⁴, -C_1-6alkylene-R¹⁴, -C_6-10arylene-R¹⁴, -NH-C_1-6alkyl-R¹⁴, and -NH-C(O)-C_1-6alkyl-R¹⁴; wherein said aryl or arylene may optionally be substituted with one or two substituents each independently selected from the group consisting of -C_1-4alkyl, halogen, and -C_1- ₄haloalkyl; if present, each R¹¹ and R¹² is independently selected from the group consisting of hydrogen, - C_1-6alkyl, -C_3-10carbocyclyl, and 3-10 membered heterocyclyl; if present, R¹³ is selected from the group consisting of hydrogen, -C_1-6alkyl, halogen, -CN, -C₃- ₁₀carbocyclyl, 3-10 membered heterocyclyl, -O-C_1-6alkyl, -O-C_3-10carbocyclyl, -O-(3-10 mem- bered heterocyclyl), -NH(C_1-6alkyl), -N(C_1-6alkyl)₂, -NH-C_3-10carbocyclyl, -N(C_1-4alkyl)-C₆- ₁₀carbocyclyl, -NH-(3-10 membered heterocyclyl), -N(C_1-4alkyl)-(3-10 membered heterocy- clyl), -C(O)-C_1-4alkyl, -C(O)-C_3-10carbocyclyl, -C(O)-(3-10 membered heterocyclyl), and - C(O)N(C_1-4alkyl)₂, wherein said alkyl, carbocyclyl or heterocyclyl may be unsubstituted or substituted with up to two substituents each independently selected from the group consisting of -C_1- ₄alkyl, oxo, halogen and -C_1-4haloalkyl; and if present, R¹⁴ is selected from the group consisting of -NH₂, -C_3-10heterocyclyl, -O- C_3-10heter- ocyclyl, -NH-C_3-10heterocyclyl, and -N(Me)-C_3-10heterocyclyl; wherein said heterocyclyl may be unsubstituted or substituted with up to three substituents each independently selected from -C_1-4alkyl, oxo, halogen and -C_1-4haloalkyl.

In some embodiments, R¹ and R⁵ are each independently selected from the group con- sisting of halogen and -C_1-4alkyl. In some embodiments, R¹ and R⁵ are each halogen. In some embodiments, R¹ and R⁵ are each chlorine. In some embodiments, R³ is selected from the group consisting of C_1-6alkyl, -O-C_1-6alkyl, phenyl, or 5-6 membered heteroaromatic, said phenyl or heteroaromatic being unsubstituted or substituted by one or two C_1-4 alkyl groups. In some embodiments, R³ is -O-C_1-4alkyl. In some embodiments, R³ is -O-CH₃. In some embodiments, R² and R⁴ are each hydrogen. In some embodiments, R⁶ is selected from the group consisting of hydrogen, halogen, C_1-4alkyl and -O-C_1-4alkyl. In some embodiments, R⁶ is hydrogen. In some embodiments, R⁷ is selected from the group consisting of hydrogen, -C_1-6alkyl, C_3-10car- bocyclyl, -O-C_3-10carbocyclyl, -NH-C_3-10carbocyclyl, C_3-10heterocyclyl, -O-C_3-10heterocyclyl and -NH-C_3-10heterocyclyl. In some embodiments, R⁷ is hydrogen. In some embodiments, R⁸ is selected from the group consisting of hydrogen, -C_1-4alkylene-R¹³, -O-C_1-4alkylene-R¹³ and -O-R¹³, and R¹³ is selected from the group consisting of hydrogen, -C_1-6alkyl, C_3-10carbocyclyl, -O-C_3-10carbocyclyl, -NH-C_3-10carbocyclyl, C_3-10heterocyclyl, -O- C_3-10heterocyclyl and -NH- C_3-10heterocyclyl. In some embodiments, R⁸ is hydrogen. In some embodiments, R⁹ is hydro- gen. In some embodiments, R⁸ and R⁹ are each hydrogen. In some embodiments, R¹⁰ is selected from the group consisting of hydrogen, C_1-6alkyl, C_1-6haloalkyl, C_6-10aryl, -R¹⁴, -C_1-6alkylene- R¹⁴ and -C_6-10arylene-R¹⁴, wherein said aryl or arylene may optionally be substituted with one or two substituents each independently selected from the group consisting of C_1-4alkyl, halogen and C_1-4haloalkyl. In some embodiments, R¹⁰ is -CH₃. In some embodiments, n is 1. In some embodiments, X is O. In some embodiments, n is 1 and X is O. In some embodiments, R¹ and R⁵ are chlorine, R³ is -OCH₃, and R² and R⁴ are each hydrogen.

In some embodiments, the compound of Formula (I) is

(la).

In some embodiments, the compound of Formula (I) is

(Ic).

In some embodiments, the compound of Formula (I) is

(Id).

In some embodiments, n is 0. In some embodiments, X is S. In some embodiments, n is 0 and X is S. In some embodiments, R¹ and R⁵ are chlorine, R³ is -OCH₃, and R² and R⁴ are each hydrogen.

In some embodiments, the compound of Formula (I) is

(lb).

In a further aspect, there is provided a pharmaceutical composition comprising the compound or salt as described herein, and a pharmaceutically acceptable excipient. In some embodiments, the pharmaceutical composition further comprises a therapeutic agent. In some embodiments, the further therapeutic agent is an anti-cancer agent. In some embodiments, the further therapeutic agent is selected from the group consisting of ipilimumab, bevacizumab, pemetrexed, platinum chemotherapeutics, a taxane, etoposide, and gemcitabine. In some em- bodiments, the pharmaceutical composition further comprising a checkpoint inhibitor. In some embodiments, the checkpoint inhibitor is a PD-1 or PD-L1 inhibitor. In some embodiments, the checkpoint inhibitor is selected from the group consisting of nivolumab, pembrolizumab, pi- dilizumab, AMP-224, TSR-042, BMS-936559, BMS-1001, BMS-1166, BGB-A317, atezoli- zumab, avelumab, cemiplimab, and durvalumab. In some embodiments, the checkpoint inhibi- tor is a CHEK2 inhibitor. In some embodiments, the checkpoint inhibitor is selected from the group consisting of CCT241533 and BML-277.

In a further aspect, there is provided a compound or salt as described herein, or a phar- maceutical composition as described herein, for use in therapy. In some embodiments, the com- pound or salt as described herein, or a pharmaceutical composition as described herein is for use in immunotherapy. In some embodiments, the compound or salt as described herein, or a pharmaceutical composition as described herein is for use in preventing or treating cancer.

In a further aspect, there is provided a method of reducing PD-L1 expression, com- prising contacting a compound or salt as described herein, or a pharmaceutical composition as described herein, with a PAK enzyme.

In a further aspect, there is provided a method of decreasing the binding of PD-L1 to PD-1, comprising contacting a compound or salt as described herein, or a pharmaceutical com- position as described herein, with a PAK enzyme.

In a further aspect, there is provided a method of decreasing CHEK2 expression, com- prising contacting a compound or salt as described herein, or a pharmaceutical composition as described herein, with a PAK enzyme.

In a further aspect, there is provided a method of inhibiting CHEK2, comprising con- tacting a compound or salt as described herein, or a pharmaceutical composition as described herein, with a PAK enzyme.

In a further aspect, there is provided a method of preventing or treating cancer in a subject, comprising administering an effective amount of the compound or salt as described herein, or a pharmaceutical composition as described herein, to the subject.

In a further aspect, there is provided a method of immunotherapy, comprising admin- istering an effective amount of the compound or salt as described herein, or a pharmaceutical composition as described herein, to the subject.

In a further aspect, there is provided use of a compound or salt as described herein, in the preparation of a medicament for use in immunotherapy. In a further aspect, there is provided use of a compound or salt as described herein, in the preparation of a medicament for use in preventing or treating cancer. In some embodiments, the compound or salt, or pharmaceutical composition, is administered in combination with a further therapeutic agent. In some embodiments, the further therapeutic agent is an anti-cancer agent. In some embodiments, the further therapeutic agent is selected from the group consisting of ipilimumab, bevacizumab, pemetrexed, platinum chemotherapeutics, a taxane, etoposide, and gemcitabine. In some embodiments, the compound or salt, or pharmaceutical composition, further comprises a checkpoint inhibitor. In some embodiments, the checkpoint inhibitor is a PD-1 or PDL-1 inhibitor. In some embodiments, the checkpoint inhibitor is selected from the group consisting of nivolumab, pembrolizumab, pidilizumab, AMP-224, TSR-042, BMS- 936559, BMS-1001, BMS-1166, BGB-A317, atezolizumab, avelumab, cemiplimab, and dur- valumab. In some embodiments, the checkpoint inhibitor is a CHEK2 inhibitor. In some em- bodiments, the checkpoint inhibitor is selected from the group consisting of CCT241533 and BML-277. In some embodiments, the cancer is selected from the group consisting of mela- noma, kidney cancer, bladder cancer, head and neck cancer, Hodgkin’s lymphoma, pancreatic cancer, breast cancer, gastric cancer, glioma, hepatocellular cancer, cholangiocarcinoma, lung cancer, ovarian cancer, osteosarcoma, oesophageal squamous cell cancer, colon cancer, pros- tate cancer, colorectal cancer, brain glioblastoma, liver cancer, and bile duct cancer. In some embodiments, the cancer is selected from the group consisting of melanoma, kidney cancer, bladder cancer, head and neck cancer, Hodgkin’s lymphoma, and lung cancer. In some embod- iments, the cancer is selected from the group consisting of pancreatic cancer, breast cancer, gastric cancer, glioma, hepatocellular cancer, cholangiocarcinoma, lung cancer, ovarian cancer, osteosarcoma, oesophageal squamous cell cancer, colon cancer, and prostate cancer.

Brief Description of the Drawings

Figure 1 shows an image of compound PF03758309 bound to PAK4.

Figure 2 shows an image of compound FRAX486 bound to PAK4.

Figure 3 shows an image of compound G5555 bound to PAK1.

Figure 4 shows a chart showing PAK4 kinase activity at different concentrations of compound la in a cell-free kinase assay, together with a negative and positive control (PF03758309).

Figure 5 shows a Western Blot demonstrating that Compound la dose-dependently in- hibited the expression of PD-L1 in DLD1 cells.

Figure 6 shows the efficacy of Compound la on CHEK2 inhibition. Figure 7 shows the efficacy of Compound la in combination with Gemcitabine. Figure 7A shows the efficacy of Gemcitabine, alone and in combination with Compound la, against tumour volume over 21 days. Figure 7B shows the efficacy of Gemcitabine, alone and in com- bination with Compound la, against tumour volume over 31 days. Figure 7C shows the efficacy of Gemcitabine, alone and in combination with Compound la, against advanced tumours (size = 100 mm³). Figure 7D shows the efficacy of Gemcitabine, alone and in combination with Compound la, against tumour volume following intra-tumour injection.

Figure 8 shows that Compound la in combination with Gemcitabine increases various immunological biomarkers.

Figure 9 shows that a prodrug derivative of Compound la is able to inhibit pancreatic cell proliferation with a comparable potency to Compound la.

Description

General Definitions

Unless specifically defined otherwise, all technical and scientific terms used herein shall be taken to have the same meaning as commonly understood by one of ordinary skill in the art (e.g., chemistry, medicinal chemistry and the like).

As used herein, the term “and/or”, e.g., “X and/or Y” shall be understood to mean either "X and Y" or "X or Y" and shall be taken to provide explicit support for both meanings or for either meaning.

As used herein, the term about, unless stated to the contrary, refers to +/- 20%, more preferably +/- 10%, of the designated value.

As used herein, singular forms “a”, “an” and “the” include plural aspects, unless the context clearly indicates otherwise.

Throughout this specification, the word “comprise”, or variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.

As used herein, the term “subject” refers to any organism susceptible to a disease or condition. For example, the subject can be a mammal, primate, livestock (e.g., sheep, cow, horse, pig), companion animal (e.g., dog, cat), or laboratory animal (e.g., mouse, rabbit, rat, guinea pig, hamster). In one example, the subject is a mammal. In one embodiment, the subject is human. In one embodiment, the disease or condition is cancer. As used herein, the term “treating” includes alleviation of the symptoms associated with a specific disorder or condition and eliminating said symptoms. For example, as used herein, the term “treating cancer" refers to alleviating the symptoms associated with cancer and elimi- nating said symptoms. In one embodiment, the term “treating cancer" refers to a reduction in cancerous tumour size. In one embodiment, the term “treating cancer" refers to an increase in progression-free survival.

As used herein, the term “prevention” includes prophylaxis of the specific disorder or condition. For example, as used herein, the term “preventing cancer" refers to preventing the onset or duration of the symptoms associated with cancer. In one example, the term “preventing cancer" refers to slowing or halting the progression of the cancer. In one example, the term “preventing cancer" refers to slowing or preventing metastasis.

As would be understood by the person skilled in the art, a compound of Formula (I) or salt thereof would be administered in a therapeutically effective amount. The term “therapeuti- cally effective amount”, as used herein, refers to a compound of Formula (I) or salt thereof being administered in an amount sufficient to alleviate or prevent to some extent one or more of the symptoms of the disorder or condition being treated. The result can be the reduction and/or alleviation of the signs, symptoms, or causes of a disease or condition, or any other desired alteration of a biological system. In one embodiment, the term “therapeutically effective amount” refers to a compound of Formula (I) or salt thereof being administered in an amount sufficient to result in a reduction of symptoms associated with cancer. In one embodiment, the term “therapeutically effective amount” refers to a compound of Formula (I) or salt thereof being administered in an amount sufficient to result in a reduction in cancerous tumour size. The term, an “effective amount”, as used herein, refers to an amount of a compound of Formula (I) or salt thereof effective to achieve a desired pharmacologic effect or therapeutic improve- ment without undue adverse side effects or to achieve a desired pharmacologic effect or thera- peutic improvement with a reduced side effect profile. By way of example only, therapeutically effective amounts may be determined by routine experimentation, including but not limited to a dose escalation clinical trial. The term “therapeutically effective amount” includes, for exam- ple, a prophylactically effective amount. In one embodiment, a prophylactically effective amount is an amount sufficient to prevent cancer. It is understood that “an effective amount” or “a therapeutically effective amount” can vary from subject to subject, due to variation in metabolism of the compound and any of age, weight, general condition of the subject, the con- dition being treated, the severity of the condition being treated, and the judgment of the pre- scribing physician. Thus, it is not always possible to specify an exact “effective amount”. How- ever, an appropriate “effective amount” in any individual case may be determined by one of ordinary skill in the art using routine experimentation. Where more than one therapeutic agent is used in combination, a “therapeutically effective amount” of each therapeutic agent can refer to an amount of the therapeutic agent that would be therapeutically effective when used on its own, or may refer to a reduced amount that is therapeutically effective by virtue of its combi- nation with one or more additional therapeutic agents.

The compounds of the present disclosure may contain chiral (asymmetric) centers or the molecule as a whole may be chiral. The individual stereoisomers (enantiomers and diastereoi- somers) and mixtures of these are within the scope of the present invention.

The following definitions apply to the terms as used throughout this specification, unless otherwise limited in specific instances.

As used herein, the term “halogen” means fluorine, chorine, bromine, or iodine.

As used herein, the term “alkyl” encompasses both straight chain (i.e., linear) and branched chain hydrocarbon groups. Examples of alkyl groups include methyl, ethyl, n-propyl, iso-propyl, n-butyl, t-butyl, i-butyl, sec-butyl, pentyl, and hexyl groups. In one example, the alkyl group is of one to six carbon atoms (i.e. C_1-6alkyl).

As used herein, the term “alkoxy” refers to the group -O-alkyl, where “alkyl” is as de- scribed above. Examples of alkoxy groups include methoxy, ethoxy, propoxy, and butoxy groups. In one example, the alkoxy group is of one to six carbon atoms (i.e. -O-C_1-6alkyl).

As used herein, the term “alkenyl” refers to both straight and branched chain unsaturated hydrocarbon groups with at least one carbon-carbon double bond. Examples of alkenyl groups include ethenyl, propenyl, butenyl, pentenyl, and hexenyl groups. In one example, the alkenyl group is of two to six carbon atoms (i.e. C_2-6alkenyl).

As used herein, the term “alkynyl” refers to both straight and branched chain unsaturated hydrocarbon groups with at least one carbon-carbon triple bond. Examples of alkynyl groups include ethynyl, propynyl, butynyl, pentynyl, and hexynyl groups. In one example, the alkynyl group is of two to six carbon atoms (i.e. C_2-6alkynyl).

As used herein, the term “haloalkyl” refers to an alkyl group having at least one halogen substituent, where “alkyl” and “halogen” are as described above. Similarly, the term “dihaloal- kyl” means an alkyl group having two halogen substituents, and the term “trihaloalkyl” means an alkyl group having three halogen substituents. Examples of haloalkyl groups include fluo- romethyl, chloromethyl, bromomethyl, iodomethyl, fluoropropyl, and fluorobutyl groups. Ex- amples of dihaloalkyl groups include difluoromethyl and difluoroethyl groups. Examples of trihaloalkyl groups include trifluoromethyl and trifluoroethyl groups. In one example, the haloalkyl group is of one to six carbon atoms (i.e. C_1-6haloalkyl).

As used herein, the term “oxyhaloalkyl” refers to the group -O-haloalkyl, where “haloal- kyl” is as described above. Examples of -O-haloalkoxy groups include -O-fluoromethyl, -O- chloromethyl, -O-bromomethyl, -O-iodomethyl, -O-fluoropropyl, and -O-fluorobutyl groups. In one example, the oxyhaloalkyl group is of one to six carbon atoms (i.e. -O-C_1-6haloalkyl).

As used herein, the term “carbocyclyl” refers to an aromatic or non-aromatic cyclic group of carbon atoms. A carbocyclyl group may, for example, be monocyclic or polycyclic (i.e. bicyclic, tricyclic). A polycyclic carbocyclyl group may contain fused rings. In one exam- ple, the carbocyclyl group is of three to ten carbon atoms (i.e. C_3-10carbocyclyl).

Examples of monocyclic non-aromatic carbocyclyl groups include cyclopropyl, cyclobutyl, cyclopentyl, cyclopentenyl, cyclohexyl, cyclohexenyl, cycloheptyl, and cyclooctyl groups. Ar- omatic carbocyclyl groups include phenyl and napthalenyl.

As used herein, the term “heterocyclyl” refers to an aromatic or non-aromatic cyclic group which is analogous to a carbocyclic group, but in which from one to three of the carbon atoms is/are replaced by one or more heteroatoms independently selected from nitrogen, oxy- gen, or sulfur. A heterocyclyl group may, for example, be monocyclic or polycyclic (e.g. bicy- clic). A polycyclic heterocyclyl may for example contain fused rings. In a bicyclic heterocyclyl group there may be one or more heteroatoms in each ring, or heteroatoms only in one of the rings. A heteroatom may be N, O, or S. Heterocyclyl groups containing a suitable nitrogen atom include the corresponding N-oxides. In one example, the heterocyclyl group is of three to ten atoms (i.e. 3-10-membered heterocyclyl). Examples of monocyclic non-aromatic heterocyclyl groups include aziridinyl, azetidinyl, pyrrolidinyl, imidazolidinyl, pyrazolidinyl, piperidinyl, piperazinyl, tetrahydrofuranyl, tetrahydropyranyl, morpholinyl, thiomorpholinyl and azepanyl. Examples of bicyclic heterocyclyl groups in which one of the rings is non-aromatic include dihydrobenzofuranyl, indanyl, indolinyl, isoindolinyl, tetrahydroisoquinolinyl, tetrahydro- quinolyl, and benzoazepanyl. Examples of monocyclic aromatic heterocyclyl groups (also re- ferred to as monocyclic heteroaryl groups) include furanyl, thienyl, pyrrolyl, oxazolyl, thia- zolyl, imidazolyl, oxadiazolyl, thiadiazolyl, pyridyl, triazolyl, triazinyl, pyridazyl, isothiazolyl, isoxazolyl, pyrazinyl, pyrazolyl, and pyrimidinyl. Examples of bicyclic aromatic heterocyclyl groups (also referred to as bicyclic heteroaryl groups) include quinoxalinyl, quinazolinul, pyr- idopyrazinyl, benzoxazolyl, benzothiophenyl, benzimidazolyl, naphthyridinyl, quinolinyl, ben- zofuranyl, indolyl, benzothiazolyl, oxazolyl[4,5-b]pyridyl, pyridopyrimidinyl, isoquinolinyl, and benzohydroxazole. The present disclosure relates to compounds of Formula (I) and salts thereof. Salts may be formed in the case of embodiments of the compound of Formula (I) which contain a suitable acidic or basic group. Suitable salts of the compound of Formula (I) include those formed with organic or inorganic acids or bases. As used herein, the phrase “pharmaceutically acceptable salt” refers to pharmaceutically acceptable organic or inorganic salts. Exemplary acid addition salts include, but are not limited to, sulfate, citrate, acetate, oxalate, chloride, bro- mide, iodide, nitrate, bisulfate, phosphate, acid phosphate, isonicotinate, lactate, salicylate, acid citrate, tartrate, oleate, tannate, pantothenate, bitartrate, ascorbate, succinate, maleate, gentis- inate, fumarate, gluconate, glucuronate, saccharate, formate, benzoate, glutamate, methanesul- fonate, ethanesulfonate, benzenesulfonate, p-toluenesulfonate, and pamoate (i.e., 1,1'-meth- ylene-bis-(2-hydroxy-3-naphthoate)) salts. Exemplary base addition salts include, but are not limited to, ammonium salts, alkali metal salts, for example those of potassium and sodium, alkaline earth metal salts, for example those of calcium and magnesium, and salts with organic bases, for example dicyclohexylamine, N-methyl-D-glucomine, morpholine, thiomorpholine, piperidine, pyrrolidine, a mono-, di- or tri-lower alkylamine, for example ethyl-, tert-butyl-, diethyl-, diisopropyl-, triethyl-, tributyl- or dimethyl -propylamine, or a mono-, di- or trihy- droxy lower alkylamine, for example mono-, di- or triethanolamine. A pharmaceutically ac- ceptable salt may involve the inclusion of another molecule such as an acetate ion, a succinate ion or other counterion. The counterion may be any organic or inorganic moiety that stabilizes the charge on the parent compound. Furthermore, a pharmaceutically acceptable salt may have more than one charged atom in its structure. Instances where multiple charged atoms are part of the pharmaceutically acceptable salt can have multiple counter ions. Hence, a pharmaceuti- cally acceptable salt can have one or more charged atoms and/or one or more counterion. It will also be appreciated that nonpharmaceutically acceptable salts also fall within the scope of the present disclosure since these may be useful as intermediates in the preparation of pharmaceu- tically acceptable salts or may be useful during storage or transport.

Those skilled in the art of organic and/or medicinal chemistry will appreciate that many organic compounds can form complexes with solvents in which they are reacted or from which they are precipitated or crystallized. These complexes are known as "solvates". For example, a complex with water is known as a "hydrate". As used herein, the phrase “pharmaceutically acceptable solvate” or “solvate” refer to an association of one or more solvent molecules and a compound of the present disclosure. Examples of solvents that form pharmaceutically accepta- ble solvates include, but are not limited to, water, isopropanol, ethanol, methanol, DMSO, ethyl acetate, acetic acid, and ethanolamine. It will be understood that the present disclosure encom- passes solvated forms, including hydrates, of the compounds of formula (I) and salts thereof.

Those skilled in the art of organic and/or medicinal chemistry will appreciate that the compounds of Formula (I) and salts thereof may be present in amorphous form, or in a crystal- line form. It will be understood that the present disclosure encompasses all forms and poly- morphs of the compounds of Formula (I) and salts thereof.

Compounds of Fonnula (I)

In one aspect, there is provided a compound of Formula (I) or a salt thereof:

Formula (I); wherein R¹, R³, and R⁵ are each independently selected from the group consisting of hydrogen, halogen, C_1-6alkyl, -O-C_1-6alkyl, C_1-6haloalkyl, -O-C_1-6haloalkyl, C_2-6alkenyl, C_2-6alkynyl, C₃- ₁₀carbocyclyl, 3-10 membered heterocyclyl, -CN, -OR¹¹, -SR¹¹, -NR¹¹R¹², -COR¹¹, -CO₂R¹¹, - CONR¹¹R¹², -NR¹¹COR¹², -SO₂R¹¹, -SO₂NR¹¹R¹², and -NR¹¹SO₂R¹², wherein said alkyl, alkenyl, alkynyl, carbocyclyl or heterocyclyl may be unsubstituted or substituted with one or more substituents each independently selected from the group consisting of halogen, C_1-4alkyl, 0-C_1-4alkyl, C_1-4haloalkyl, -O-C_1-4haloalkyl, -CN, - OR¹¹, -SR¹¹, -NR¹¹R¹², -COR¹¹, -CO₂R¹¹, -CONR¹¹R¹², -NR¹¹COR¹², -SO₂R¹¹, - SO₂NR¹¹R¹², and -NR¹¹SO₂R¹²;

R² and R⁴ are each independently selected from the group consisting of hydrogen, halogen, C_1- ₄alkyl, -O-C_1-4alkyl, C_1-4haloalkyl and -O-C_1-4haloalkyl; n is an integer of from 0 to 2;

X is S, O, or NH;

R⁶ is selected from the group consisting of hydrogen, halogen, C_1-4alkyl, -O-C_1-4alkyl, C_1-4haloalkyl and -O-C_1-4haloalkyl; R⁷ is selected from the group consisting of hydrogen, halogen, -CN, -C_1-6alkyl, C_3-10carbocy- clyl, C_3-10heterocyclyl, -O-C_1-6alkyl, -O-C_3-10carbocyclyl, -O-(3-10 membered heterocyclyl), - NH(C_1-6alkyl), -N(C_1-6alkyl)₂, -NH-C_3-10carbocyclyl, -N(C_1-4alkyl)-C_6-10carbocyclyl, -NH-(3- 10 membered heterocyclyl), -N(C_1-4alkyl)-(3-10 membered heterocyclyl), -C(O)-C_1-4alkyl, - C(O)-C_3-10carbocyclyl, -C(O)-(3-10 membered heterocyclyl), and -C(O)N(C_1-4alkyl)₂, wherein said alkyl, carbocyclyl or heterocyclyl may be unsubstituted or substituted with up to two substituents each independently selected from the group consisting of C_1- ₄alkyl, oxo, halogen and C_1-4haloalkyl;

R⁸ is selected from the group consisting of hydrogen, -C_1-8alkyl, -O-C_1-8alkyl, -C_1-4alkylene- R¹³, -O-C_1-4alkylene-R¹³ and -O-R¹³;

R⁹ is selected from the group consisting of hydrogen and halogen;

R¹⁰ is selected from the group consisting of hydrogen, C_1-6alkyl, C_1-6haloalkyl, C_6-10aryl, -R¹⁴, -C_1-6alkylene-R¹⁴, -C_6-10arylene-R¹⁴, -NH-C_1-6alkyl-R¹⁴' and -NH-C(O)-C_1-6alkyl-R¹⁴; wherein said aryl or arylene may optionally be substituted with one or two substituents each independently selected from the group consisting of C_1-4alkyl, halogen and C_1- ₄haloalkyl; if present, each R¹¹ and R¹² is independently selected from the group consisting of hydrogen, C_1-6alkyl, C_3-10carbocyclyl, and 3-10 membered heterocyclyl; if present, R¹³ is selected from the group consisting of hydrogen, -C_1-6alkyl, halogen, -CN, C₃- ₁₀carbocyclyl, 3-10 membered heterocyclyl, -O-C_1-6alkyl, -O-C_3-10carbocyclyl, -O-(3-10 mem- bered heterocyclyl), -NH(C_1-6alkyl), -N(C_1-6alkyl)₂, -NH-C_3-10carbocyclyl, -N(C_1-4alkyl)-C₆- ₁₀carbocyclyl, -NH-(3-10 membered heterocyclyl), -N(C_1-4alkyl)-(3-10 membered heterocy- clyl), -C(O)-C_1-4alkyl, -C(O)-C_3-10carbocyclyl, -C(O)-(3-10 membered heterocyclyl), and - C(O)N(C_1-4alkyl)₂, wherein said alkyl, carbocyclyl or heterocyclyl may be unsubstituted or substituted with up to two substituents each independently selected from the group consisting of C_1- ₄alkyl, oxo, halogen and C_1-4haloalkyl; and if present, R¹⁴ is selected from the group consisting of -NH₂, C_3-10heterocyclyl, -O- C_3-10heter- ocyclyl, -NH-C_3-10heterocyclyl and -N(Me)-C_3-10heterocyclyl; wherein said heterocyclyl may be unsubstituted or substituted with up to three substituents each independently selected from C_1-4alkyl, oxo, halogen and C_1-4haloalkyl.

R¹, R³, and R⁵ of Formula (I) are each independently selected from the group consisting of hydrogen, halogen, C_1-6alkyl, -O-C_1-6alkyl, C_1-6haloalkyl, -O-C_1-6haloalkyl, C_2-6alkenyl, C_2- 6alkynyl, C_3-10carbocyclyl, 3-10 membered heterocyclyl, -CN, -OR¹¹, -SR¹¹, -NR¹¹R¹², -COR¹¹, -CO₂R¹¹, -CONR¹¹R¹², -NR¹¹COR¹², -SO₂R¹¹, -SO₂NR¹¹R¹², and -NR¹¹SO₂R¹², wherein said alkyl, alkenyl, alkynyl, carbocyclyl or heterocyclyl may be unsubstituted or substituted with one or more substituents each independently selected from the group consisting of halogen, C_1- ₄alkyl, O-C_1-4alkyl, C_1-4haloalkyl, -O-C_1-4haloalkyl, -CN, -OR¹¹, -SR¹¹, -NR¹¹R¹², -COR¹¹, - CO₂R¹¹, -CONR¹¹R¹², -NR¹¹COR¹², -SO₂R¹¹, -SO₂NR¹¹R¹², and -NR¹¹SO₂R¹². That is, R¹, R³ and R⁵ may each be the same, or independently different substituents, as described above.

In some embodiments, R¹, R³ and R⁵ of Formula (I) are each independently selected from the group consisting of hydrogen, halogen, C_1-6alkyl, -O-C_1-6alkyl, C_1-6haloalkyl, -O-C_1- ₆haloalkyl. In some embodiments, R¹, R³ and R⁵ are each independently selected from the group consisting of halogen, C_1-6alkyl, -O-C_1-6alkyl. In some embodiments, R¹, R³ and R⁵ are each independently selected from the group consisting of halogen and -O-C_1-6alkyl. In some embod- iments, R¹ is halogen. In some embodiments, R¹ is chlorine. In some embodiments, R⁵ is halo- gen. In some embodiments, R⁵ is chlorine. In some embodiments, R³ is methoxy.In some em- bodiments, R³ is selected from the group consisting of C_1-6alkyl, -O-C_1-6alkyl, phenyl, or 5-6 membered heteroaromatic, said phenyl or heteroaromatic being unsubstituted or substituted by one or two C_1-4 alkyl groups.

In some embodiments, R¹ is halogen, R³ is -O-C_1-6alkyl, and R⁵ is halogen. In some embodiments, R¹ is chlorine, R³ is methoxy, and R⁵ is chlorine.

R² and R⁴ of Formula (I) are each independently selected from the group consisting of hydrogen, halogen, C_1-4alkyl, -O-C_1-4alkyl, C_1-4haloalkyl and -O-C_1-4haloalkyl. That is, R² and R⁴ of Formula (I) may each be the same, or independently different substituents, as described above. In some embodiments, R² and R⁴ are each independently selected from the group con- sisting of hydrogen, halogen, and -O-C_1-4alkyl. In some embodiments, R² and R⁴ are each in- dependently selected from the group consisting of hydrogen and halogen. In some embodi- ments, R² is hydrogen. In some embodiments, R⁴ is hydrogen. In some embodiments, R² is hydrogen and R⁴ is hydrogen.

In some embodiments, R² is hydrogen, R⁴ is hydrogen, and R¹, R³ and R⁵ are each in- dependently selected from the group consisting of hydrogen, halogen, C_1-6alkyl, -O-C_1-6alkyl, C_1-6haloalkyl, -O-C_1-6haloalkyl. In some embodiments, R² is hydrogen, R⁴ is hydrogen, and R¹, R³ and R⁵ are each independently selected from the group consisting of halogen, C_1-6alkyl, -O- C_1-6alkyl. In some embodiments, R² is hydrogen, R⁴ is hydrogen, and R¹, R³ and R⁵ are each independently selected from the group consisting of halogen and -O-C_1-6alkyl. In some embod- iments, R² is hydrogen, R⁴ is hydrogen, R¹ is halogen, R³ is -O-C_1-6alkyl, and R⁵ is halogen. In some embodiments, R² is hydrogen, R⁴ is hydrogen, R¹ is chlorine, R³ is methoxy, and R⁵ is chlorine. n is an integer of from 0 to 2. In some embodiments, n is 0. In such an instance where n is 0, it will be understood by the person skilled in the art that the six-membered benzene ring of Formula (I) is directly bonded to the five-membered ring of Formula (I). In some embodi- ments, n is 1. In such an instance where n is 1, it will be understood by the person skilled in the art that the six-membered benzene ring of Formula (I) is bonded to the five-membered ring of Formula (I) through one carbon atom, e.g. via a -CH₂- group. In some embodiments, n is 2. In such an instance where n is 2, it will be understood by the person skilled in the art that the six- membered benzene ring of Formula (I) is bonded to the five-membered ring of Formula (I) through two carbon atoms, e.g. via a -CH₂CH₂- group.

X of Formula (I) is S, O, or NH. In some embodiments, X is S. In some embodiments, X is O. In some embodiments, X is NH.

In some embodiments, X is S, O, or NH, and n is 0. In some embodiments, X is S, O, or NH, and n is 1. In some embodiments, X is S, O, or NH, and n is 2. In some embodiments, n is 0 and X is O or S. In some embodiments, n is 1 and X is O or S. In some embodiments, n is 2 and X is O or S. In some embodiments, n is 0, and X is S. In some embodiments, n is 1, and X is O.

R⁶ of Formula (I) is selected from the group consisting of hydrogen, halogen, C_1-4alkyl, -O-C_1-4alkyl, C_1-4haloalkyl and -O-C_1-4haloalkyl. In some embodiments, R⁶ is selected from the group consisting of hydrogen, halogen, C_1-4alkyl, and -O-C_1-4alkyl. In some embodiments, R⁶ is selected from the group consisting of hydrogen and halogen. In some embodiments, R⁶ is hydrogen.

R⁷ of Formula (I) is selected from the group consisting of hydrogen, halogen, -CN, - C_1-6alkyl, C_3-10carbocyclyl, C_3-10heterocyclyl, -O-C_1-6alkyl, -O-C_3-10carbocyclyl, -O-(3-10 membered heterocyclyl), -NH(C_1-6alkyl), -N(C_1-6alkyl)₂, -NH-C_3-10carbocyclyl, -N(C_1-4alkyl)- C_6-10carbocyclyl, -NH-(3-10 membered heterocyclyl), -N(C_1-4alkyl)-(3-10 membered hetero- cyclyl), -C(O)-C_1-4alkyl, -C(O)-C_3-10carbocyclyl, -C(O)-(3-10 membered heterocyclyl), and - C(O)N(C_1-4alkyl)₂, wherein said alkyl, carbocyclyl or heterocyclyl may be unsubstituted or substituted with up to two substituents each independently selected from the group consisting of C_1-4alkyl, oxo, halogen and C_1-4haloalkyl.

In some embodiments. R⁷ is selected from the group consisting of hydrogen, -C_1-6al- kyl, C_3-10carbocyclyl, -O-C_3-10carbocyclyl, -NH-C_3-10carbocyclyl, C_3-10heterocyclyl, -O- C₃- ₁₀heterocyclyl and -NH-C_3-10heterocyclyl. In some embodiments, R⁷ is selected from the group consisting of hydrogen, -C_1-6al- kyl, C_3-10carbocyclyl, -O-C_3-10carbocyclyl, -NH-C_3-10carbocyclyl, C_3-10heterocyclyl, -O- C₃- ₁₀heterocyclyl and -NH-C_3-10heterocyclyl, wherein said carbocyclyl is selected from the group consisting of C_1-6cycloalkyl, C_1-6cycloalkenyl, phenyl, which cycloalkyl, cycloalkenyl or phe- nyl may optionally be substituted with one or two substituents selected from the group consist- ing of halogen, C_1-2alkyl and C_1-2haloalkyl; and wherein said heterocyclyl is selected from the group consisting of morpholinyl, thiazolyl, piperidinyl, pyrrolidinyl, furyl, imidazolyl and pyr- idinyl, and said morpholinyl, thiazolyl, piperidinyl, pyrrolidinyl, furyl, imidazolyl or pyridinyl may optionally be substituted with one or two substituents selected from the group consisting of halogen, C_1-2alkyl and C_1-2haloalkyl.

In some embodiments, R⁷ is selected from the group consisting of:

and

In some embodiments, R⁷ is hydrogen.

In some embodiments, n is 0 or 1, X is O or S, R⁶ is selected from the group consisting of hydrogen and halogen, and R⁷ is selected from the group consisting of hydrogen, -C_1-6alkyl, C_3-10carbocyclyl, -O-C_3-10carbocyclyl, -NH-C_3-10carbocyclyl, C_3-10heterocyclyl, -O- C_3-10heter- ocyclyl and -NH-C_3-10heterocyclyl.

In some embodiments, n is 0 or 1, X is O or S, R⁶ is selected from the group consisting of hydrogen and halogen, and R⁷ is selected from the group consisting of hydrogen, -C_1-6alkyl, C_3-10carbocyclyl, -O-C_3-10carbocyclyl, -NH-C_3-10carbocyclyl, C_3-10heterocyclyl, -O- C_3-10heter- ocyclyl and -NH-C_3-10heterocyclyl, wherein said carbocyclyl is selected from the group con- sisting of C_1-6cycloalkyl, C_1-6cycloalkenyl, phenyl, which cycloalkyl, cycloalkenyl or phenyl may optionally be substituted with one or two substituents selected from the group consisting of halogen, C_1-2alkyl and C_1-2haloalkyl; and wherein said heterocyclyl is selected from the group consisting of morpholinyl, thiazolyl, piperidinyl, pyrrolidinyl, furyl, imidazolyl and pyr- idinyl, and said morpholinyl, thiazolyl, piperidinyl, pyrrolidinyl, furyl, imidazolyl or pyridinyl may optionally be substituted with one or two substituents selected from the group consisting of halogen, C_1-2alkyl and C_1-2haloalkyl.

In some embodiments, n is 0 or 1, X is O or S, R⁶ is selected from the group consisting of hydrogen and halogen, and R⁷ is selected from the group consisting of:

In some embodiments, n is 0 or 1, X is O or S, R⁶ is hydrogen, and R⁷ is hydrogen. In some embodiments, n is 1, X is O, R⁶ is hydrogen, and R⁷ is hydrogen.

In some embodiments, n is 0, X is S, R⁶ is hydrogen, and R⁷ is hydrogen. In some embodiments, R² is hydrogen, R⁴ is hydrogen, R¹, R³ and R⁵ are each inde- pendently selected from the group consisting of hydrogen, halogen, C_1-6alkyl, -O-C_1-6alkyl, C_1- ₆haloalkyl, -O-C_1-6haloalkyl, n is 0 or 1, X is O or S, R⁶ is selected from the group consisting of hydrogen and halogen, and R⁷ is selected from the group consisting of hydrogen, -C_1-6alkyl, C_3-10carbocyclyl, -O-C_3-10carbocyclyl, -NH-C_3-10carbocyclyl, C_3-10heterocyclyl, -O- C_3-10heter- ocyclyl and -NH-C_3-10heterocyclyl.

In some embodiments, R² is hydrogen, R⁴ is hydrogen, R¹, R³ and R⁵ are each inde- pendently selected from the group consisting of halogen, C_1-6alkyl, -O-C_1-6alkyl, n is 0 or 1, X is O or S, R⁶ is selected from the group consisting of hydrogen and halogen, and R⁷ is selected from the group consisting of hydrogen, -C_1-6alkyl, C_3-10carbocyclyl, -O-C_3-10carbocyclyl, -NH- C_3-10carbocyclyl, C_3-10heterocyclyl, -O- C_3-10heterocyclyl and -NH-C_3-10heterocyclyl, wherein said carbocyclyl is selected from the group consisting of C_1-6cycloalkyl, C_1-6cycloalkenyl, phe- nyl, which cycloalkyl, cycloalkenyl or phenyl may optionally be substituted with one or two substituents selected from the group consisting of halogen, C_1-2alkyl and C_1-2haloalkyl; and wherein said heterocyclyl is selected from the group consisting of morpholinyl, thiazolyl, pi- peridinyl, pyrrolidinyl, furyl, imidazolyl and pyridinyl, and said morpholinyl, thiazolyl, piper- idinyl, pyrrolidinyl, furyl, imidazolyl or pyridinyl may optionally be substituted with one or two substituents selected from the group consisting of halogen, C_1-2alkyl and C_1-2haloalkyl.

In some embodiments, R² is hydrogen, R⁴ is hydrogen, and R¹, R³ and R⁵ are each independently selected from the group consisting of halogen and -O-C_1-6alkyl, n is 0 or 1, X is O or S, R⁶ is selected from the group consisting of hydrogen and halogen, and R⁷ is selected from the group consisting of:

H

,0, N N

Cl

H Cl .Cl

N

, and

In some embodiments, R² is hydrogen, R⁴ is hydrogen, R¹ is chlorine, R³ is methoxy, R⁵ is chlorine, n is 0 or 1, X is O or S, R⁶ is hydrogen, and R⁷ is hydrogen.

R⁸ is selected from the group consisting of hydrogen, -C_1-8alkyl, -O-C_1-salkyl, -C_1- ₄alkylene-R¹³, -O-C_1-4alkylene-R¹³ and -O-R¹³.

In some embodiments, R⁸ is selected from the group consisting of -CM alkyl and -Cl- C_1-4alkyl. in some embodiments, R⁸ is selected from the group consisting of -C_1-4alkylene-R¹³, - 0-C_1-4alkylene-R¹³ and -O-R¹³, and R¹³ is selected from the group consisting of hydrogen, -C_1- ₆alkyl, C_3-10carbocyclyl, -O-C_3-10carbocyclyl, -NH-C_3-10carbocyclyl, C_3-10heterocyclyl, -O- C₃- ₁₀heterocyclyl and -NH-C_3-10heterocyclyl.

In some embodiments, R⁸ is selected from the group consisting of -C_1-4alkylene-R¹³, - 0-C_1-4alkylene-R¹³ and -O-R¹³, and R¹³ is selected from the group consisting of hydrogen, -C_1- ₆alkyl, C_3-10carbocyclyl, -O-C_3-10carbocyclyl, -NH-C_3-10carbocyclyl, C_3-10heterocyclyl, -O- C₃- ₁₀heterocyclyl and -NH-C_3-10heterocyclyl, wherein said carbocyclyl is selected from the group consisting of C_1-6cycloalkyl, C_1-6cycloalkenyl, phenyl, which cycloalkyl, cycloalkenyl or phe- nyl may optionally be substituted with one or two substituents selected from the group consist- ing of halogen, C_1-2alkyl and C_1-2haloalkyl; and wherein said heterocyclyl is selected from the group consisting of morpholinyl, thiazolyl, piperidinyl, pyrrolidinyl, furyl, imidazolyl and pyr- idinyl, and said morpholinyl, thiazolyl, piperidinyl, pyrrolidinyl, furyl, imidazolyl or pyridinyl may optionally be substituted with one or two substituents selected from the group consisting of halogen, C_1-2alkyl and C_1-2haloalkyl.

In some embodiments, R⁸ is selected from the group consisting of -C_1-4alkylene-R¹³, - O- C_1-4alkylene-R¹³ and -O-R¹³, and R¹³ is selected from the group consisting of:

and

In some embodiments, R⁸ is hydrogen.

R⁹ is selected from the group consisting of hydrogen and halogen. In some embodi- ments, R⁹ is hydrogen. In some embodiments, R⁹ is halogen.

R¹⁰ is selected from the group consisting of hydrogen, C_1-6alkyl, C_1-6haloalkyl, C₆- 1₀aryl, -R¹⁴, -C_1-6alkylene-R¹⁴, -C_6-10arylene-R¹⁴, -NH-C_1-6alkyl-R^14, and -NH-C(O)-C_1-6alkyl- R¹⁴, wherein said aryl or arylene may optionally be substituted with one or two substituents each independently selected from the group consisting of C_1-4alkyl, halogen and C_1-4haloalkyl.

In some embodiments, R¹⁰ is selected from the group consisting of C_1-6alkyl, C_1- ₆haloalkyl, and -C_6-10arylene-R¹⁴, wherein said arylene may optionally be substituted with one substituent selected from the group consisting of C_1-4alkyl, halogen and C_1-4haloalkyl; and wherein R¹⁴ is selected from the group consisting of C_3-10heterocyclyl, -O- C_3-10heterocyclyl, NH- C_3-10heterocyclyl and N(Me)- C_3-10heterocyclyl; wherein said heterocyclyl may be unsub- stituted or substituted with up to three substituents each independently selected from C_1-4alkyl, oxo, halogen and C_1-4haloalkyl.

In some embodiments, R¹⁰ is -C_6-10arylene-R¹⁴, wherein said arylene may optionally be substituted with one substituent selected from the group consisting of C_1-4alkyl, halogen and C_1-4haloalkyl; and wherein R¹⁴ is selected from the group consisting of C_3-10heterocyclyl, -O- C_3-10heterocyclyl, NH- C_3-10heterocyclyl and N(Me)- C_3-10heterocyclyl; wherein said heterocy- clyl is selected from the group consisting of thiomorpholinyl, piperazinyl, piperidinyl, pyrroli- dinyl or morpholinyl, and wherein said heterocyclyl may be unsubstituted or substituted with up to three substituents each independently selected from C_1-4alkyl, oxo, halogen and C_1- ₄haloalkyl.

In some embodiments, R¹⁰ is -C_6-10arylene-R¹⁴, wherein said arylene may optionally be substituted with one substituent selected from the group consisting of C_1-4alkyl, halogen and C_1-4haloalkyl; and wherein R¹⁴ is selected from the group consisting of C_3-10heterocyclyl, -O- C_3-10heterocyclyl, NH- C_3-10heterocyclyl andN(Me)- C_3-10heterocyclyl; wherein said heterocy- clyl is selected from the group consisting of

In some embodiments, R¹⁰ is selected from the group consisting of

In some embodiments, R¹⁰ is C_1-6alkylene. In some embodiments R¹⁰ is methyl.

In some embodiments, R¹⁰ is -NH-C_1-6alkyl-R¹⁴. In some embodiments, R¹⁰ is -NH-

CH₃-CH₃-R¹⁴.

In some embodiments, R¹⁰ is -NH-C(O)-C_1-6alkyl-R¹⁴. In some embodiments, R¹⁰ is - NH-C(O)-CH₃-R¹⁴.

In some embodiments, R¹⁰ is -NH-C_1-6alkyl-R¹⁴ and R¹⁴ is -NH₂. In some embodi- ments, R¹⁰ is -NH-C(O)-C_1-6alkyl-R¹⁴ and R¹⁴ is -NH₂.

In some embodiments, R⁸ is selected from the group consisting of hydrogen, -C_1- ₄alkylene-R¹³, -O-C_1-4alkylene-R¹³ and -O-R¹³, and R¹³ is selected from the group consisting of hydrogen, -C_1-6alkyl, C_3-10carbocyclyl, -O-C₃- locarbocyclyl, -NH-C_3-10carbocyclyl, C_3-10heter- ocyclyl, -O- C_3-10heterocyclyl and -NH-C_3-10heterocyclyl, R⁹ is hydrogen, and R¹⁰ is selected from the group consisting of C_1-6alkyl, C_1-6haloalkyl, and -C_6-10arylene-R¹⁴, wherein said ar- ylene may optionally be substituted with one substituent selected from the group consisting of C_1-4alkyl, halogen and C_1-4haloalkyl; and wherein R¹⁴ is selected from the group consisting of C_3-10heterocyclyl, -O- C_3-10heterocyclyl, NH- C_3-10heterocyclyl and N(Me)- C_3-10heterocyclyl; wherein said heterocyclyl may be unsubstituted or substituted with up to three substituents each independently selected from C_1-4alkyl, oxo, halogen and C_1-4haloalkyl.

In some embodiments, R⁸ is selected from the group consisting of hydrogen, -C_1-4al- kylene-R¹³, -O-C_1-4alkylene-R¹³ and -O-R¹³, and R¹³ is selected from the group consisting of hydrogen, -C_1-6alkyl, C_3-10carbocyclyl, -O-C_3-10carbocyclyl, -NH-C_3-10carbocyclyl, C_3-10heter- ocyclyl, -O- C_3-10heterocyclyl and -NH-C_3-10heterocyclyl, wherein said carbocyclyl is selected from the group consisting of C_1-6cycloalkyl, C_1-6cycloalkenyl, phenyl, which cycloalkyl, cyclo- alkenyl or phenyl may optionally be substituted with one or two substituents selected from the group consisting of halogen, C_1-2alkyl and C_1-2haloalkyl; and wherein said heterocyclyl is se- lected from the group consisting of morpholinyl, thiazolyl, piperidinyl, pyrrolidinyl, furyl, im- idazolyl and pyridinyl, and said morpholinyl, thiazolyl, piperidinyl, pyrrolidinyl, furyl, imidaz- olyl or pyridinyl may optionally be substituted with one or two substituents selected from the group consisting of halogen, C_1-2alkyl and C_1-2haloalkyl, R⁹ is hydrogen, and R¹⁰ is C_1-6alkylene or -C_6-10arylene-R¹⁴, wherein said arylene may optionally be substituted with one substituent selected from the group consisting of C_1-4alkyl, halogen and C_1-4haloalkyl; and wherein R¹⁴ is selected from the group consisting of C_3-10heterocyclyl, -O- C_3-10heterocyclyl, NH- C_3-10heter- ocyclyl and N(Me)- C_3-10heterocyclyl; wherein said heterocyclyl is selected from the group consisting of thiomorpholinyl, piperazinyl, piperidinyl, pyrrolidinyl or morpholinyl, and wherein said heterocyclyl may be unsubstituted or substituted with up to three substituents each independently selected from C_1-4alkyl, oxo, halogen and C_1-4haloalkyl.

In some embodiments, R⁸ is selected from the group consisting of hydrogen, -C_1-4al- kylene-R¹³, -O-C_1-4alkylene-R¹³ and -O-R¹³, and R¹³ is selected from the group consisting of hydrogen, -C_1-6alkyl, C_3-10carbocyclyl, -O-C_3-10carbocyclyl, -NH-C_3-10carbocyclyl, C_3-10heter- ocyclyl, -O- C_3-10heterocyclyl and -NH-C_3-10heterocyclyl, wherein said carbocyclyl is selected from the group consisting of C_1-6cycloalkyl, C_1-6cycloalkenyl, phenyl, which cycloalkyl, cyclo- alkenyl or phenyl may optionally be substituted with one or two substituents selected from the group consisting of halogen, C_1-2alkyl and C_1-2haloalkyl; and wherein said heterocyclyl is se- lected from the group consisting of morpholinyl, thiazolyl, piperidinyl, pyrrolidinyl, furyl, im- idazolyl and pyridinyl, and said morpholinyl, thiazolyl, piperidinyl, pyrrolidinyl, furyl, imidaz- olyl or pyridinyl may optionally be substituted with one or two substituents selected from the group consisting of halogen, C_1-2alkyl and C_1-2haloalkyl, R⁹ is hydrogen, and R¹⁰ is C_1-6alkylene or -C_6-10arylene-R¹⁴, wherein said arylene may optionally be substituted with one substituent selected from the group consisting of C_1-4alkyl, halogen and C_1-4haloalkyl; and wherein R¹⁴ is selected from the group consisting of C_3-10heterocyclyl, -O- C_3-10heterocyclyl, NH- C_3-10heter- ocyclyl and N(Me)- C_3-10heterocyclyl; wherein said heterocyclyl is selected from the group consisting of

In some embodiments, R⁸ is selected from the group consisting of hydrogen, -C_1-4al- kylene-R¹³, -O-C_1-4alkylene-R¹³ and -O-R¹³, and R¹³ is selected from the group consisting of:

In some embodiments, R⁹ is hydrogen, and R¹⁰ is methyl or is selected from the group consisting of

9 9 9

In some embodiments, R⁸ is hydrogen, R⁹ is hydrogen, and R¹⁰ is methyl.

If present each of R¹¹ and R¹² is independently selected from the group consisting of hydrogen, C_1-6alkyl, C_3-10carbocyclyl, and 3-10 membered heterocyclyl. In some embodi- ments, each of R¹¹ and R¹² is independently selected from the group consisting of hydrogen and C_1-6alkyl.

In some embodiments, R² is hydrogen, R⁴ is hydrogen, R¹, R³ and R⁵ are each inde- pendently selected from the group consisting of hydrogen, halogen, C_1-6alkyl, -O-C_1-6alkyl, C_1- ₆haloalkyl, -O-C_1-6haloalkyl, n is 0 or 1, X is O or S, R⁶ is selected from the group consisting of hydrogen and halogen, and R⁷ is selected from the group consisting of hydrogen, -C_1-6alkyl, C_3-10carbocyclyl, -O-C_3-10carbocyclyl, -NH-C₃- locarbocyclyl, C_3-10heterocyclyl, -O- C_3-10heter- ocyclyl and -NH-C_3-10heterocyclyl, R⁸ is selected from the group consisting of hydrogen, -C_1- ₄alkylene-R¹³, -O-C_1-4alkylene-R¹³ and -O-R¹³, and R¹³ is selected from the group consisting of hydrogen, -C_1-6alkyl, C_3-10carbocyclyl, -O-C_3-10carbocyclyl, -NH-C_3-10carbocyclyl, C_3-10heter- ocyclyl, -O- C_3-10heterocyclyl and -NH-C_3-10heterocyclyl, wherein said carbocyclyl is selected from the group consisting of C_1-6cycloalkyl, C_1-6cycloalkenyl, phenyl, which cycloalkyl, cyclo- alkenyl or phenyl may optionally be substituted with one or two substituents selected from the group consisting of halogen, C_1-2alkyl and C_1-2haloalkyl; and wherein said heterocyclyl is se- lected from the group consisting of morpholinyl, thiazolyl, piperidinyl, pyrrolidinyl, furyl, im- idazolyl and pyridinyl, and said morpholinyl, thiazolyl, piperidinyl, pyrrolidinyl, furyl, imidaz- olyl or pyridinyl may optionally be substituted with one or two substituents selected from the group consisting of halogen, C_1-2alkyl and C_1-2haloalkyl, R⁹ is hydrogen, and R¹⁰ is C_1-6alkylene or -C_6-10arylene-R¹⁴, wherein said arylene may optionally be substituted with one substituent selected from the group consisting of C_1-4alkyl, halogen and C_1-4haloalkyl; and wherein R¹⁴ is selected from the group consisting of C_3-10heterocyclyl, -O- C_3-10heterocyclyl, NH- C_3-10heter- ocyclyl and N(Me)- C_3-10heterocyclyl; wherein said heterocyclyl is selected from the group consisting of thiomorpholinyl, piperazinyl, piperidinyl, pyrrolidinyl or morpholinyl, and wherein said heterocyclyl may be unsubstituted or substituted with up to three substituents each independently selected from C_1-4alkyl, oxo, halogen and C_1-4haloalkyl.

In some embodiments, R² is hydrogen, R⁴ is hydrogen, R¹, R³ and R⁵ are each inde- pendently selected from the group consisting of halogen, C_1-6alkyl, -O-C_1-6alkyl, n is 0 or 1, X is O or S, R⁶ is selected from the group consisting of hydrogen and halogen, R⁷ is selected from the group consisting of hydrogen, -C_1-6alkyl, C_3-10carbocyclyl, -O-C_3-10carbocyclyl, -NH-C₃- ₁₀carbocyclyl, C_3-10heterocyclyl, -O- C_3-10heterocyclyl and -NH-C_3-10heterocyclyl, wherein said carbocyclyl is selected from the group consisting of C_1-6cycloalkyl, C_1-6cycloalkenyl, phe- nyl, which cycloalkyl, cycloalkenyl or phenyl may optionally be substituted with one or two substituents selected from the group consisting of halogen, C_1-2alkyl and C_1-2haloalkyl; and wherein said heterocyclyl is selected from the group consisting of morpholinyl, thiazolyl, pi- peridinyl, pyrrolidinyl, furyl, imidazolyl and pyridinyl, and said morpholinyl, thiazolyl, piper- idinyl, pyrrolidinyl, furyl, imidazolyl or pyridinyl may optionally be substituted with one or two substituents selected from the group consisting of halogen, C_1-2alkyl and C_1-2haloalkyl, R⁸ is selected from the group consisting of hydrogen, -C_1-4alkylene-R¹³, -O-C_1-4alkylene-R¹³ and -O-R¹³, and R¹³ is selected from the group consisting of hydrogen, -C_1-6alkyl, C_3-10carbocyclyl, -O-C_3-10carbocyclyl, -NH-C_3-10carbocyclyl, C_3-10heterocyclyl, -O- C_3-10heterocyclyl and -NH- C_3-10heterocyclyl, wherein said carbocyclyl is selected from the group consisting of C_1-6cyclo- alkyl, C_1-6cycloalkenyl, phenyl, which cycloalkyl, cycloalkenyl or phenyl may optionally be substituted with one or two substituents selected from the group consisting of halogen, C_1-2alkyl and C_1-2haloalkyl; and wherein said heterocyclyl is selected from the group consisting of mor- pholinyl, thiazolyl, piperidinyl, pyrrolidinyl, furyl, imidazolyl and pyridinyl, and said mor- pholinyl, thiazolyl, piperidinyl, pyrrolidinyl, furyl, imidazolyl or pyridinyl may optionally be substituted with one or two substituents selected from the group consisting of halogen, C_1-2alkyl and C_1-2haloalkyl, R⁹ is hydrogen, and R¹⁰ is C_1-6alkylene or -C_6-10arylene-R¹⁴, wherein said arylene may optionally be substituted with one substituent selected from the group consisting of C_1-4alkyl, halogen and C_1-4haloalkyl; and wherein R¹⁴ is selected from the group consisting of C_3-10heterocyclyl, -O- C_3-10heterocyclyl, NH- C_3-10heterocyclyl and N(Me)- C_3-10heterocy- clyl; wherein said heterocyclyl is selected from the group consisting of thiomorpholinyl, piper- azinyl, piperidinyl, pyrrolidinyl or morpholinyl, and wherein said heterocyclyl may be unsub- stituted or substituted with up to three substituents each independently selected from C_1-4alkyl, oxo, halogen and C_1-4haloalkyl.

In some embodiments, R² is hydrogen, R⁴ is hydrogen, R¹, R³ and R⁵ are each inde- pendently selected from the group consisting of halogen, C_1-6alkyl, -O-C_1-6alkyl, n is 0 or 1, X is O or S, R⁶ is selected from the group consisting of hydrogen and halogen, R⁷ is selected from the group consisting of hydrogen, -C_1-6alkyl, C_3-10carbocyclyl, -O-C_3-10carbocyclyl, -NH-C₃- ₁₀carbocyclyl, C_3-10heterocyclyl, -O- C_3-10heterocyclyl and -NH-C_3-10heterocyclyl, wherein said carbocyclyl is selected from the group consisting of C_1-6cycloalkyl, C_1-6cycloalkenyl, phe- nyl, which cycloalkyl, cycloalkenyl or phenyl may optionally be substituted with one or two substituents selected from the group consisting of halogen, C_1-2alkyl and C_1-2haloalkyl; and wherein said heterocyclyl is selected from the group consisting of morpholinyl, thiazolyl, pi- peridinyl, pyrrolidinyl, furyl, imidazolyl and pyridinyl, and said morpholinyl, thiazolyl, piper- idinyl, pyrrolidinyl, furyl, imidazolyl or pyridinyl may optionally be substituted with one or two substituents selected from the group consisting of halogen C_1-2alkyl and C_1-2haloalkyl,R⁸ is selected from the group consisting of hydrogen, -C_1-4alkylene-R¹³, -O-C_1-4alkylene-R¹³ and -O-R¹³, and R¹³ is selected from the group consisting of hydrogen, -C_1-6alkyl, C_3-10carbocyclyl, -O-C_3-10carbocyclyl, -NH-C_3-10carbocyclyl, C_3-10heterocyclyl, -O- C_3-10heterocyclyl and -NH- C_3-10heterocyclyl, wherein said carbocyclyl is selected from the group consisting of C_1-6cyclo- alkyl, C_1-6cycloalkenyl, phenyl, which cycloalkyl, cycloalkenyl or phenyl may optionally be substituted with one or two substituents selected from the group consisting of halogen, C_1-2alkyl and C_1-2haloalkyl; and wherein said heterocyclyl is selected from the group consisting of mor- pholinyl, thiazolyl, piperidinyl, pyrrolidinyl, furyl, imidazolyl and pyridinyl, and said mor- pholinyl, thiazolyl, piperidinyl, pyrrolidinyl, furyl, imidazolyl or pyridinyl may optionally be substituted with one or two substituents selected from the group consisting of halogen, C_1-2alkyl and C_1-2haloalkyl, R⁹ is hydrogen, and R¹⁰ is C_1-6alkylene or -C_6-10arylene-R¹⁴, wherein said arylene may optionally be substituted with one substituent selected from the group consisting of C_1-4alkyl, halogen and C_1-4haloalkyl; and wherein R¹⁴ is selected from the group consisting of C_3-10heterocyclyl, -O- C_3-10heterocyclyl, NH- C_3-10heterocyclyl and N(Me)- C_3-10heterocy- clyl; wherein said heterocyclyl is selected from the group consisting of

and

9 9 9

In some embodiments, R² is hydrogen, R⁴ is hydrogen, R¹ is chlorine, R³ is methoxy, R⁵ is chlorine, n is 0 or 1, X is O or S, R⁶ is hydrogen, R⁷ is hydrogen, R⁸ is hydrogen, R⁹ is hydrogen, and R¹⁰ is methyl.

In some embodiments, the compound of Formula (I) is:

(la).

In some embodiments, the compound of Formula (I) is:

(lb).

In some embodiments, the compound of Formula (I) is:

(Ic).

Compound Ic is considered a prodrug of Compound la. In some embodiments, Com- pound Ic is a prodrug of Compound la. As would be understood by the person skilled in the art, a “prodrug” is a biologically less active or inactive molecule that is capable of being metabo- lised in the body into the physiologically active drag form. A diverse array of biological en- zymes are capable of metabolising various prodrugs into their more active forms, typically through alteration or removal of a functional moiety. In this instance, it is understood that Com- pound Ic is metabolised in the body into Compound la. Accordingly, in some embodiments, Compound Ic is metabolised into Compound la.

In some embodiments, the compound of Formula (I) is:

(Id).

PAK Inhibitors

Compound la has been demonstrated to have activity as a PAK inhibitor. In some em- bodiments, a PAK inhibitor is a compound having an IC₅₀ against a PAK of at least 100 uM, at least lOuM, at least 1 uM, or at least 200 nM.

The compounds of Formula (I) are understood to exhibit selectivity for inhibition of a particular PAK sub-type, e.g. PAK4. For example, a compound of Formula (I) may selectively bind to the PAK4 enzyme, such that it inhibits, or reduces or prevents, the downstream activity of the PAK4 enzyme. Accordingly, in some embodiments, the compound of Formula (I), or salt thereof, is a selective PAK4 inhibitor. By “selective”, it is understood that the compound of Formula (I) shows a preference for binding to a particular PAK sub-type over other PAK sub- types, e.g. for PAK4 over other PAKs. In some embodiments, the compound of Formula (I) is selective for PAK4 over other PAK subtypes by at least 2-fold, at least 5-fold, or at least 10- fold.

Accordingly, the present disclosure also provides a method of inhibiting a PAK enzyme, comprising contacting a compound of Formula (I) or a salt thereof, or a pharmaceutical com- position as described herein, with a PAK enzyme. The present disclosure also provides a method of inhibiting PAK4, comprising contacting a ompound of Formula (I) or a salt thereof, or a pharmaceutical composition as described herein, with PAK4.

Therapeutic Methods and Uses

The compound of Formula (I) and salts thereof of the present disclosure, and pharma- ceutical compositions comprising the compounds of Formula (I) and salts thereof, find use in the therapy of diseases, for example cancers. Accordingly, there is also provided a compound of Formula (I) or salt thereof as described herein, or pharmaceutical composition as described herein, for use in therapy.

A compound of Formula (I) or salt thereof, or a pharmaceutical composition as de- scribed herein, finds use in the treatment of diseases for which inhibition of PAK activity, par- ticularly PAK 4 activity, provides a therapeutic effect. Such diseases include, but are not lim- ited to, cancers, infectious diseases, and neurological disorders.

Accordingly, there is provided a method of preventing or treating cancer in a subject, comprising administering an effective amount of the compound of Formula (I) or a salt thereof, or of a pharmaceutical composition as described herein, to the subject. There is also provided a compound of Formula (I) or salt thereof, or a pharmaceutical composition as described herein, for use in preventing or treating cancer. There is also provided use of a compound of Formula (I) or salt thereof, or of a pharmaceutical composition as described herein, in the manufacture of a medicament for use in preventing or treating a cancer in a subject.

In some embodiments, the cancer is a PAK-dependent cancer, in other words it is a cancer in respect of which inhibition of a PAK provides a therapeutic or prophylactic effect. In some embodiments, the cancer is a PAK4-dependent cancer, i.e. a cancer in respect of which inhibition of PAK-4 provides a therapeutic or prophylactic effect.

Examples of cancers include but are not limited to pancreatic cancer, breast cancer, gastric cancer, glioma, hepatocellular cancer, cholangioc arcinoma, lung cancer, ovarian cancer, osteosarcoma, oesophageal squamous cell cancer, colon cancer, colorectal cancer, brain glio- blastoma, melanoma, liver cancer, bile duct cancer, and prostate cancer. Lung cancer includes non-small-cell lung cancer.

The present compounds are understood not only to have anti-proliferative properties, but also to act by decreasing expression of PD-L1. One approach to cancer therapy is based on inhibiting the interaction between PD-1 and PD-L1, and preventing cancers from evading the immune system. This approach is referred to as immunotherapy, and agents which inhibit either PD-1 or PD-L1 are referred to as checkpoint inhibitors.

Similarly, the present compounds are understood to also act by decreasing expression of CHEK2. Further, the present compounds are understood to also act by inhibiting CHEK2.

Thus, the present compounds find use in immunotherapy. Examples of cancers for which the compounds are contemplated for use with also include, but are not limited to, mela- noma, kidney cancer, bladder cancer, head and neck cancer, Hodgkin’s lymphoma, colorectal cancer, brain glioblastoma, liver cancer, and bile duct cancer. In some embodiments, a com- pound of Formula (I) or salt thereof, or a pharmaceutical composition as described herein, is used in the prevention and/or treatment of pancreatic cancer. In some embodiments, a com- pound of Formula (I) or salt thereof, or a pharmaceutical composition as described herein, is used in the prevention and/or treatment of colon cancer. In some embodiments, a compound of Formula (I) or salt thereof, or a pharmaceutical composition as described herein, is used in the prevention and/or treatment of cholangiocarcinoma. In some embodiments, a compound of For- mula (I) or salt thereof, or a pharmaceutical composition as described herein, is used in the prevention and/or treatment of lung cancer. In some embodiments, a compound of Formula (I) or salt thereof, or a pharmaceutical composition as described herein, is used in the prevention and/or treatment of non-small-cell lung cancer. In some embodiments, a compound of Formula (I) or salt thereof, or a pharmaceutical composition as described herein, is used in the prevention and/or treatment of melanoma. In some embodiments, a compound of Formula (I) or salt thereof, or a pharmaceutical composition as described herein, is used in the prevention and/or treatment of kidney cancer. In some embodiments, a compound of Formula (I) or salt thereof, or a pharmaceutical composition as described herein, is used in the prevention and/or treatment of bladder cancer. In some embodiments, a compound of Formula (I) or salt thereof, or a phar- maceutical composition as described herein, is used in the prevention and/or treatment of head and neck cancer. In some embodiments, a compound of Formula (I) or salt thereof, or a phar- maceutical composition as described herein, is used in the prevention and/or treatment of Hodg- kin’ s lymphoma. In some embodiments, a compound of Formula (I) or salt thereof, or a phar- maceutical composition as described herein, is used in the prevention and/or treatment of colo- rectal cancer. In some embodiments, a compound of Formula (I) or salt thereof, or a pharma- ceutical composition as described herein, is used in the prevention and/or treatment of brain glioblastoma. In some embodiments, a compound of Formula (I) or salt thereof, or a pharma- ceutical composition as described herein, is used in the prevention and/or treatment of liver cancer. In some embodiments, a compound of Formula (I) or salt thereof, or a pharmaceutical composition as described herein, is used in the prevention and/or treatment of bile duct cancer.

In some embodiments, the cancer is selected from the group consisting of melanoma, kidney cancer, bladder cancer, head and neck cancer, Hodgkin’s lymphoma, pancreatic cancer, breast cancer, gastric cancer, glioma, hepatocellular cancer, cholangiocarcinoma, lung cancer, ovarian cancer, osteosarcoma, oesophageal squamous cell cancer, colon cancer, colorectal can- cer, brain glioblastoma, liver cancer, bile duct cancer, and prostate cancer.

In some embodiments, a compound of Formula (I) which is used in therapy (e.g. in cancer therapy) is:

(la).

(lb).

(Ic).

(Ic). which is metabolised in the body to produce Compound la.

(Id).

In some embodiments, there is provided a method of therapy comprising administering a therapeutically effective amount of a compound of Formula (I) to a patient in need thereof. In some embodiments, there is provided a method of therapy comprising administering a thera- peutically effective amount of Compound la to a patient in need thereof. In some embodiments, there is provided a method of therapy comprising administering a therapeutically effective amount of Compound lb to a patient in need thereof. In some embodiments, there is provided a method of therapy comprising administering a therapeutically effective amount of Compound Ic to a patient in need thereof. In some embodiments, there is provided a method of therapy comprising administering a therapeutically effective amount of Compound Id to a patient in need thereof.

In some embodiments, there is provided a method of therapy comprising administering a therapeutically effective amount of a prodrug of a compound of Formula (I) to a patient in need thereof. In some embodiments, there is provided a method of therapy comprising admin- istering a therapeutically effective amount of the prodrug Compound Ic to a patient in need thereof, wherein Compound Ic is metabolised following administration to produce Compound

Ia.

In some embodiments, there is provided a method of treating cancer comprising admin- istering a therapeutically effective amount of a compound of Formula (I) to a patient in need thereof. In some embodiments, there is provided a method of treating cancer comprising ad- ministering a therapeutically effective amount of Compound Ia to a patient in need thereof. In some embodiments, there is provided a method of treating cancer comprising administering a therapeutically effective amount of Compound lb to a patient in need thereof. In some embod- iments, there is provided a method of treating cancer comprising administering a therapeutically effective amount of Compound Ic to a patient in need thereof. In some embodiments, there is provided a method of treating cancer comprising administering a therapeutically effective amount of Compound Id to a patient in need thereof.

In some embodiments, there is provided a method of treating cancer comprising admin- istering a therapeutically effective amount of a prodrug of a compound of Formula (I) to a patient in need thereof. In some embodiments, there is provided a method of treating cancer comprising administering a therapeutically effective amount of the prodrug Compound Ic to a patient in need thereof, wherein Compound Ic is metabolised following administration to pro- duce Compound la.

Immunotherapy and Combination Treatments

Compound la has been demonstrated to inhibit PD-L1 expression. In some embodi- ments there is provided a method of decreasing PD-L1 expression, comprising contacting a compound of Formula (I) or a salt thereof, or a pharmaceutical composition comprising the compound or salt, with a PAK enzyme. As discussed above, checkpoint inhibitors are under- stood to act by blocking the interaction and/or binding of PD-1 with one or both of its ligands, PD-L1 and PD-L2. In some embodiments, there is provided a method of decreasing the binding of PD-L1 to PD-1, comprising contacting a compound of Formula (I) or a salt thereof, or a pharmaceutical composition comprising the compound or salt, with a PAK enzyme.

In some embodiments, the PAK enzyme is a PAK4 enzyme. In one example, there is provided a method of decreasing PD-L1 expression, comprising contacting a compound of For- mula (I) or a salt thereof, or a pharmaceutical composition comprising the compound or salt, with a PAK4 enzyme. In some embodiments, there is provided a method of decreasing the binding of PD-L1 to PD-1, comprising contacting a compound of Formula (I) or a salt thereof, or a pharmaceutical composition comprising the compound or salt, with a PAK4 enzyme.

Compound la has also been demonstrated to inhibit Checkpoint Kinase 2 (CHEK2) ex- pression. CHEK2 is a tumour suppression gene, in which mutations to the gene are understood to cause a wide range of cancers. CHEK2 encodes the protein CHEK2, which is a versatile and multifunctional kinase that regulates the cell’s response to DNA damage by phosphorylating a number of distinct cellular substrates. On the basis of its role during DNA damage response, CHEK2 has been suggested as an anticancer therapy target. Compound la has also been demon- strated to inhibit CHEK2. In some embodiments there is provided a method of decreasing CHEK2 expression, comprising contacting a compound of Formula (I) or a salt thereof, or a pharmaceutical composition comprising the compound or salt, with a PAK enzyme. In some embodiments there is provided a method of inhibiting CHEK2, comprising contacting a com- pound of Formula (I) or a salt thereof, or a pharmaceutical composition comprising the com- pound or salt, with a PAK enzyme.

In particular, it is understood that anticancer therapy is greatly enhanced by CHEK2 inhibition, as CHEK2 inhibition may sensitize the tumour to DNA-damaging agents used in chemotherapy. Therefore, CHEK2 inhibitors could protect healthy tissues and sensitize the tu- mour to chemotherapy.

Combination therapies, whereby both immune checkpoint inhibition and modulation of the tumour microenvironment are achieved, may for example prove a useful combination in treating cancer types that have developed resistance to immune checkpoint inhibition alone.

Combination therapy will be understood to mean the combined administration of two or more therapies. It will be understood that it is not necessary to administer such therapies simultaneously or via the same administration route. Instead, it will be understood that refer- ence to a combination therapy refers to the two or more therapies being prescribed for use to a patient in need thereof. For example, the two or more therapies may be administered simulta- neously, sequentially, and/or separately. The therapies may for example be administered peri- odically relative to each other (e.g. at a weekly interval from each other).

Accordingly, in some embodiments there is provided a compound of Formula (I) or a salt thereof, in combination with a further therapeutic agent. In some embodiments, there is provided a pharmaceutical formulation comprising the compound of Formula (I) or a salt thereof, further comprising a further therapeutic agent.

The further therapeutic agent may for example be any agent that is capable of modulat- ing the tumour microenvironment such that the effects of immune checkpoint inhibition re- sistance are reduced. The further therapeutic agent may be, for example, any agent that is used in combination therapy with checkpoint inhibitors.

In some embodiments, a PAK inhibitor, for example a compound of Formula (I) or salt thereof, is used in a combination with a further therapeutic agent which is used in combination with a checkpoint inhibitor such as pembrolizumab or nivolumab. In such combinations, the PAK inhibitor may used in combination with a further therapeutic agent, for example a cyto- toxic agent and/or an agent that serves to modulate the tumour microenvironment.

In one example, the further therapeutic agent is an anti-cancer agent. That is, an anti- cancer agent that has demonstrated anti-cancer, or chemotherapeutic, activity. In some embod- iments, the further therapeutic agent is a monoclonal antibody. In one example, the further ther- apeutic agent is ipilimumab. In one example, the further therapeutic agent is bevacizumab. In some embodiments, the anti-cancer agent is a chemotherapeutic. In one example, the further therapeutic agent is pemetrexed. In one example, the further therapeutic agent is gemcitabine. In one example, the further therapeutic agent is etoposide. In some embodiments, the further therapeutic agent is a platinum chemotherapeutic. In one example, the further therapeutic agent is cisplatin. In one example, the further therapeutic agent is oxaliplatin. In one example, the further therapeutic agent is carboplatin. In one example, the further therapeutic agent is nedapla- tin. In some embodiments, the further therapeutic agent is a taxane. In one example, the further therapeutic agent is paclitaxel. In one example, the further therapeutic agent is nab-paclitaxel. In one example, the further therapeutic agent is cabazitaxel. In one example, the further thera- peutic agent is docetaxel.

There is also provided a combination therapy comprising one or more PAK inhibitors, for example, a compound of Formula (I) or a salt thereof, and one or more further therapeutic agents. In some embodiments, there is provided a combination therapy comprising one or more PAK4 inhibitors, for example, a compound of Formula (I) or a salt thereof, and one or more further therapeutic agents. As an example, compound la may be used in a combination therapy with one or more further therapeutic agents. In one example, a combination therapy comprises a compound of Formula (I) or a salt thereof and one or more therapeutic agents. In one example, a combination therapy comprises compound la or a salt thereof and one or more further thera- peutic agents.

Alternatively, in some embodiments, a checkpoint inhibitor is used in combination with a PAK inhibitor, for example a compound of Formula (I) or a salt thereof. In some embodi- ments, a checkpoint inhibitor is used in combination with a PAK4 inhibitor, for example a compound of Formula (I) or a salt thereof.

Accordingly, there is provided a combination therapy comprising one or more check- point inhibitors and one or more PAK inhibitors, for example, a compound of Formula (I) or a salt thereof. In one example, there is provided a combination therapy comprising one or more checkpoint inhibitors and one or more PAK4 inhibitors, for example, a compound of Formula (I) or a salt thereof. As an example, compound la may be used in a combination therapy with one or more checkpoint inhibitors. In one example, a combination therapy comprises a com- pound of Formula (I) or a salt thereof and one or more checkpoint inhibitors. In one example, a combination therapy comprises compound la or a salt thereof and one or more checkpoint inhibitors.

In some embodiments there is provided a compound of Formula (I) or a salt thereof, in combination with a checkpoint inhibitor. In some aspects, there is provided a pharmaceutical composition comprising a compound of Formula (I) or salt thereof, further comprising a check- point inhibitor. In some embodiments, the checkpoint inhibitor is a PD-1 or PD-L1 inhibitor. In some embodiments, the checkpoint inhibitor is nivolumab. In one example, the checkpoint inhibitor is pembrolizumab. In some embodiments, the checkpoint inhibitor is pidilizumab. In some embodiments, the checkpoint inhibitor is AMP-224. In some embodiments, the check- point inhibitor is TSR-042. In some embodiments, the checkpoint inhibitor is BMS-936559. In some embodiments, the checkpoint inhibitor is BMS-1001. In some embodiments, the check- point inhibitor is BMS- 1166. In some embodiments, the checkpoint inhibitor is BGB-A317. In some embodiments, the checkpoint inhibitor is atezolizumab. In one example, the checkpoint inhibitor is avelumab. In some embodiments, the checkpoint inhibitor is cemiplimab. In some embodiments, the checkpoint inhibitor is durvalumab. In some embodiments, the checkpoint inhibitor is a compound that reduces CHEK2 expression. In some embodiments, the checkpoint inhibitor is a CHEK2 inhibitor. In some embodiments, the checkpoint inhibitor is CCT241533. In some embodiments, the checkpoint inhibitor is BML-277.

Compositions

Whilst a compound of Formula (I) or salt thereof may in some embodiments be admin- istered alone, it is more typically administered as part of a pharmaceutical composition or for- mulation. Thus, the present disclosure also provides a pharmaceutical composition comprising a compound of Formula (I) or salt thereof and a pharmaceutically acceptable excipient. The pharmaceutical composition comprises one or more pharmaceutically acceptable diluents, car- riers or excipients (collectively referred to herein as “excipient” materials).

The present disclosure also provides pharmaceutical formulations or compositions, both for veterinary and for human medical use, which comprise compounds of Formula (I) of the present disclosure or a pharmaceutically acceptable salt thereof, with one or more pharmaceu- tically acceptable carriers, and optionally any other therapeutic ingredients, stabilisers, or the like. The carrier(s) must be pharmaceutically acceptable in the sense of being compatible with the other ingredients of the formulation and not unduly deleterious to the recipient thereof.

Examples of pharmaceutical formulations include those suitable for oral, parenteral (in- cluding subcutaneous, intradermal, intramuscular, intravenous, and intraarticular), inhalation (including fine particle dusts or mists that may be generated by means of various types of me- tered dose pressurised aerosols), nebulisers or insufflators, rectal, intraperitoneal and topical (including dermal, buccal, sublingual, and intraocular) administration, although the most suit- able route may depend upon, for example, the condition and disorder of the recipient.

The pharmaceutical formulations may conveniently be presented in unit dosage form and may be prepared by any of the methods well known in the art of pharmacy. All methods include the step of brining a compound of Formula (I) or salt thereof into association with the excipient that constitutes one or more necessary ingredients. In general, the formulations are prepared by uniformly and intimately bringing into association the active ingredient with liquid carriers or finely divided solid carriers or both, and then, if necessary, shaping the product into the desired formulation.

In some embodiments, that composition is formulated for oral delivery. For example, pharmaceutical formulations of the present invention suitable for oral administration may be presented as discrete units such as capsules, cachets, pills or tablets each containing a predeter- mined amount of the active ingredient; as a powder or granules, as a solution or a suspension in an aqueous liquid or non-aqueous liquid, for example as elixirs, tinctures, suspensions or syrups; or as an oil-in- water liquid emulsion or a water-in-oil liquid emulsion. A compound of Formula (I) may also be presented as a bolus, electuary or paste.

A tablet may be made for example by compression or moulding, optionally with one or more accessory ingredients. Compressed tablets may be prepared by compressing in a suitable machine the active ingredient in a free-flowing form such as a powder or granules, optionally mixed with a binder, lubricant, inert diluent, lubricating, surface active, or dispersing agent. Moulded tablets may be made by moulding in a suitable machine a mixture of the powdered compound moistened with an inert liquid diluent. The tablets may be optionally coated or scored, and may be formulated so as to provide slow or controlled release of the compound of Formula (I). The compound of Formula (I) can, for example, be administered in a form suitable for immediate release or extended release. Immediate release or extended release can be achieved by the use of suitable pharmaceutical compositions comprising a compound of For- mula (I) or, particularly in the case of extended release, by the use of devices such as subcuta- neous implants or osmotic pumps. A compound of Formula (I) may also be administered lipo- somally.

Exemplary compositions for oral administration include suspensions which can contain, for example, microcrystalline cellulose for imparting bulk, alginic acid or sodium alginate as a suspending agent, methylcellulose as a viscosity enhancer, and sweeteners or flavouring agents such as those well known in the art; and immediate release tablets which can contain, for ex- ample, microcrystalline cellulose, dicalcium phosphate, starch, magnesium stearate, calcium sulfate, sorbitol, glucose and/or lactose and/or other excipients, binders, extenders, disinte- grants, diluents, and lubricants such as those known in the art. Suitable binders include starch, gelatin, natural sugars such as glucose or beta-lactose, com sweeteners, natural and synthetic gums such as acacia, tragacanth or sodium alginate, carboxymethylcellulose, polyethylene gly- col, waxes, and the like. Disintegrators include without limitation, starch, methylcellulose, agar, bentonite, xanthan gum, and the like. A compound of Formula (I) can also be delivered through the oral cavity by sublingual and/or buccal administration. Moulded tablets, compressed tablets, or freeze-dried tablets are exemplary forms that may be used. Exemplary compositions include those formulating a compound of Formula (I) with fast dissolving diluents such as mannitol, lactose, sucrose and/or cyclodextrins. Also included in such formulations may be high molec- ular weight excipients such as cellulose (avicel) or polyethylene glycols (PEGs). Such formu- lations can also include an excipient to aid mucosal adhesion such as hydroxyl propyl cellulose (HPC), hydroxyl propyl methyl cellulose (HPMC), sodium carboxy methyl cellulose (SCMC), maleic anhydride copolymer, and agents to control release such as polyacrylic copolymer. Lub- ricants, glidants, flavours, colouring agents, and stabilisers may also be added for ease of fab- rication and use. Lubricants used in these dosage forms include sodium oleate, sodium stearate, magnesium stearate, sodium benzoate, sodium acetate, sodium chloride, and the like. For oral administration in liquid form, the oral drug components can be combined with any oral, non- toxic, pharmaceutically acceptable inert carrier such as ethanol, glycerol, water, and the like.

In some embodiments, the composition is formulated for parenteral delivery. Formula- tions for parenteral administration include aqueous and non-aqueous sterile injections solutions which may contain anti-oxidants, buffers, bacteriostats, and solutes that render the formulation isotonic with the blood of the intended recipient; and aqueous and non-aqueous sterile suspen- sions which may include suspending agents and thickening agents. The formulations may be presented in unit-dose or multi-dose containers, for example, sealed ampoules and vials, and may be stored in a freeze-dried condition requiring only the addition of the sterile liquid carrier, for example saline or water-for-injection, immediately prior to use. Extemporaneous injection solutions and suspensions may be prepared from sterile powders, granules and tablets of the kind previously described. Exemplary compositions for parenteral administration include in- jectable solutions or suspensions which can contain, for example, suitable non-toxic, parenter- ally acceptable diluents or solvents, such as mannitol, 1.3-butanediol, water, Ringer’s solution, an isotonic sodium chloride solution, or other suitable dispersing or wetting and suspending agents, including synthetic mono- or diglycerides, and fatty acids, including oleic acid, or Cremaphor. For example, in one embodiment, the formulation may be a sterile, lyophilized compo- sition that is suitable for reconstitution in an aqueous vehicle prior to injection. In one embod- iment, a formulation suitable for parenteral administration conveniently comprises a sterile aqueous preparation of the compound of Formula (I), which may for example be formulated to be isotonic with the blood of the recipient.

The compounds of Formula (I) of the present disclosure may for example be formulated in compositions including those suitable for inhalation to the lung, by aerosol, or parenteral (including intraperitoneal, intravenous, subcutaneous, or intramuscular injection) administra- tion. The compositions may conveniently be presented in unit dosage form and may be prepared by any of the methods well known in the art of pharmacy. All methods include the step of bringing the compound of Formula (I) into association with a carrier that constitutes one or more accessory ingredients. In general, the compositions are prepared by bringing the com- pound of Formula (I) into association with a liquid carrier to form a solution or a suspension, or alternatively, bring the compound of Formula (I) into association with formulation compo- nents suitable for forming a solid, optionally a particulate product, and then, if warranted, shap- ing the product into a desired delivery form. Solid formulations of the present disclosure, when particulate, will typically comprise particles with sizes ranging from about 1 nanometer to about 500 microns. In general, for solid formulations intended for intravenous administration, parti- cles will typically range from about 1 nm to about 10 microns in diameter. The composition may contain compounds of Formula (I) of the present disclosure that are nanoparticulate having a particulate diameter of below 1000 nm, for example, between 5 and 1000 nm, especially 5 and 500 nm, more especially 5 to 400 nm, such as 5 to 50 nm and especially between 5 and 20 nm. In one example, the composition contains compounds of Formula (I) with a mean size of between 5 and 20nm. In some embodiments, the compound of Formula (I) is polydispersed in the composition, with PDI of between 1.01 and 1.8, especially between 1.01 and 1.5, and more especially between 1.01 and 1.2. In one example, the compounds of Formula (I) are monodis- persed in the composition.

It should be understood that in addition to the ingredients particularly mentioned above, the formulations may include other agents conventional in the art having regard to the type of formulation in question, for example, those suitable for oral administration may include fla- vouring agents.

The compositions of the present disclosure may also include polymeric excipients/ad- ditives or carriers, e.g., polyvinylpyrrolidones, derivatised celluloses such as hydroxymethyl- cellulose, hydroxyethylcellulose, and hydroxypropylmethylcellulose, Ficolls (a polymeric sugar), hydroxyethylstarch (HES), dextrates (e.g., cyclodextrins, such as 2-hydroxypropyl-β- cyclodextrin and sulfobutylether-β-cyclodextrin), polyethylene glycols, and pectin. The com- positions may further include diluents, buffers, citrate, trehalose, binders, disintegrants, thick- eners, lubricants, preservatives (including antioxidants), inorganic salts (e.g., sodium chloride), antimicrobial agents (e.g., benzalkonium chloride), sweeteners, antistatic agents, sorbitan es- ters, lipids (e.g., phospholipids such as lecithin and other phosphatidylcholines, phosphatidyl- ethanolamines, fatty acids and fatty esters, steroids (e.g., cholesterol)), and chelating agents (e.g., EDTA, zinc and other such suitable cations). Other pharmaceutical excipients and/or ad- ditives suitable for use in the compositions according to the present disclosure are listed in "Remington: The Science & Practice of Pharmacy", 19.sup.th ed., Williams & Williams, (1995), and in the "Physician's Desk Reference", 52.sup.nd ed., Medical Economics, Montvale, N.J. (1998), and in "Handbook of Pharmaceutical Excipients", Third Ed., Ed. A. H. Kibbe, Pharmaceutical Press, 2000.

Dosages

The amount of active ingredient that is required to achieve a therapeutic effect will, of course, vary with the particular compound, the route of administration, the subject under treat- ment, including the type, species, age, weight, sex, and medical condition of the subject being treated, and the renal and hepatic function of the subject, and the particular condition, disorder or disease being treated, as well as its severity. An ordinary skilled physician or clinician can readily determine and prescribe the effective amount of the drug required to prevent or treat the condition, disorder or disease.

Dosages of a compound of Formula (I) or salt thereof, when used for the indicated ef- fects, will range between, for example, about 0.01 mg per kg of body weight per day (mg/kg/day) to about 1000 mg/kg/day. In some embodiments, the dosage of a compound of Formula (I) or salt thereof is between about 0.01 and 1000, 0.1 and 500, 0.1 and 100, 1 and 50 mg/kg/day. In some embodiments, the dosage of a compound of Formula (I) or salt thereof is between about 0.01 and 1000 mg/kg/day. In some embodiments, the dosage of a compound of Formula (I) or salt thereof is between about 0.1 and 100 mg/kg/day. In some embodiments, the dosage of a compound of Formula (I) or salt thereof is greater than about 0.01, 0.1, 1, 10, 20, 50, 75, 100, 500, 1000 mg/kg/day. In some embodiments, the dosage of a compound of Formula (I) or salt thereof is greater than about 0.01 mg/kg/day. In some embodiments, the dosage of a compound of Formula (I) or salt thereof is less than about 5000, 1000, 75, 50, 20, 10, 1, 0.1 mg/kg/day. In some embodiments, the dosage of a compound of Formula (I) or salt thereof is less than about 1000 mg/kg/day.

A compound of Formula (I) or salt thereof may for example be administered as a single daily dose, or otherwise the total daily dosage may be administered in divided doses of two, three, or four times daily. In some embodiments, the compound of Formula (I) or salt thereof may be dosed less frequently than once per day, for example once per two days, three days, four days, five days, six days, or once per week.

If administered intravenously, an infusion of the compound over a period of time may be used, for example. Furthermore, a compound of Formula (I) or salt thereof may be admin- istered in intranasal form via topical use of suitable intranasal vehicles, or via transdermal routes, using those forms of transdermal skin patches well known to those of ordinary skill in the art. To be administered in the form of a transdermal delivery system, the dosage administra- tion will, of course, be continuous rather than intermittent throughout the dosage regimen.

Combination Therapy

Whilst a compound of Formula (I) or salt thereof may be used as the sole active agent in a medicament, as discussed above it is also possible for a compound of Formula (I) or salt thereof to be used in combination with one or more further therapeutic agents. Accordingly, in some embodiments, a compound of Formula (I) or salt thereof is used in combination with one or more further therapeutic agents. The present disclosure therefore also provides a combina- tion of a compound of Formula (I) or salt thereof and a further therapeutic agent. The present disclosure also provides a pharmaceutical composition comprising a combination of a com- pound of Formula (I) or salt thereof, a further therapeutic agent, and a pharmaceutically ac- ceptable excipient. Such one or more further therapeutic agents may for example be anti-cancer agents. Drugs are often coadministered with other drags during chemotherapy. In some embod- iments, a compound of Formula (I) or salt thereof is used in combination with one or more further anti-cancer agents.

The compound of Formula (I) or salt thereof and the one or more further pharmaceuti- cally active agents may be administered simultaneously, subsequently or separately. For exam- ple, they may be administered as part of the same composition, or by administration of separate compositions. The one or more further pharmaceutically active agents may for example be anti- cancer agents for therapy of pancreatic cancer, colon cancer, cholangiocarcinoma, lung cancer, melanoma, colorectal cancer, brain glioblastoma, liver cncer, or bile duct cancer.

The further therapeutic agents, when employed in combination with a compound of Formula (I) or salt thereof, may be used for example in those amounts indicated in the Physi- cians’ Desk Reference or as otherwise determined by one of ordinary skill in the art.

Synthesis of Compounds of Formula (I)

Numerous synthetic routes to the compounds of Formula (I) can be devised by any per- son skilled in the art and the possible synthetic routes described below are not intended to be limiting. Possible synthetic routes for the compounds of Formula (I) are shown schematically below. Where appropriate, any initially produced compound of Formula (I) can be converted into another compound of Formula (I) by known methods.

A compound of Formula (I) of the present disclosure may for example be prepared by any suitable method, for example by a) reacting a compound of Formula (II) with a compound of Formula (IIΙ)

(II) (IIΙ) (I) wherein X and n are as defined above, and R¹ to R¹⁰ are as defined above or may be a protected version thereof, Y is a halide or a pseudohalide (e.g. -OTf), and Z is a boronic acid or boronic ester group (e.g. such as a pinacol ester); and, if required, b) deprotecting the product of step a).

Step a) may be carried out under suitable conditions, e.g. Suzuki coupling conditions, using a base such as potassium phosphate, a palladium catalyst (e.g. Pd(dppf)CI₂ CH₂CI₂, and a suitable solvent such as 1,4-dioxane, e.g. at a temperature in the range of from room temper- ature to 120°C.

Step b) may be carried out using deprotection conditions suitable for any protecting group or groups used. A compound of Formula (I) may also be made, for example by a’) reacting a compound of Formula (TV) with a compound of Formula (V)

(IV) (V) (I) wherein X and n are as defined above, and R¹ to R¹⁰ are as defined above or may be a protected version thereof, and K is a halide or a pseudohalide (e.g. -OTf); and, if required b’) deprotecting the product of step a’).

Step a) may be carried out under suitable conditions, e.g. using a base such as potassium acetate, a palladium catalyst (e.g. Ρd(ΟΑc)₂), and a suitable solvent such as dimethylacetamide, e.g. at a temperature in the range of from 60°C to 180°C.

Step b’) may be carried out using deprotection conditions suitable for any protecting group or groups used.

The present disclosure will now be described with reference to the following examples which illustrate some particular aspects of the present disclosure. However, it is to be under- stood that the particularity of the following description of the present disclosure is not to su- persede the generality of the preceding description of the present disclosure.

Examples

Example 1: Design of Inhibitor Compounds

Some inhibitors of PAKs have been developed and the crystal structures of the complexes between these inhibitors and PAK kinases have been available (Rudolph et al, 2015). Using the experimental structures of the inhibitors G-5555 bound to PAK1 (Ndubaku et al, 2015), FRAX486 bound to PAK4 (Zhang et al, 2018) and PF-3758309 to PAK1 (Staben et al, 2014) (as shown in Figures 1-3), a new series of compound were designed which could bind into the ATP binding site of PAK1 and PAK4 kinases, so as to inhibit the kinase activities of PAK1 and/or PAK4. These compounds designed included compound la, compound lb, and related structures of Formula (I). The pyrimidine and -NH of the compounds of Formula (I) are understood to form two typical hydrogen bonds to the backbone of hinge region residue Leu347 ofPAKl and Leu398 of PAK4 kinase catalytic domain, so as to inhibit the ATP-PAK4 binding.

Synthesis Examples

General Methods

All solvents used were commercially available and were used without further purifica- tion. Reactions were typically run using anhydrous solvents under an inert atmosphere of nitro- gen.

Proton NMR spectra was recorded using a Broker Plus 400 NMR Spectrometer; The deuterated solvent (DMSO-d₆) contained typically 0.03% to 0.05% v/v tetramethylsilane, which was used as the reference signal (set at ™ 0.00 for 1H).

LCMS analyses were performed on a SHIMADZU LCMS consisting of an UFLC 20- AD and LCMS 2020 MS detector. The column was used was a OBD C18 Column, 30 x 150mm 5 pm. The instrument using reverse-phase conditions (acetonitrile / water, containing 10 mmol/L TFA).

Example 2: Synthesis of Compound la

5-r5-rf2.6-dichloro-4-methoxvphenvl)methvllfuran-2-vll-N-methvlpvrimidin-2-amine

Chemical Formula: C₁₇H₁₅CI₂N_3O2 Exact Mass: 363 Molecular Weight: 364

Step 1. 5-Bromo-N-methylpyrimidin-2-amine

A solution of 5-bromo-2-chloropyrimidine (10.0 g, 51.7 mmol) and a solution of CH₃NH₂ (31.0 mL, 2M in THF) in EtOH (50.0 mL) was refluxed for 16 h at 80 °C under nitrogen atmosphere. The mixture was allowed to cool down to 25 °C. The resulting mixture was concentrated under vacuum. The residue was purified by silica gel column chromatography (eluting with 1:3 ethyl acetate/petroleum ether) to afford 5-bromo-N-methylpyrimidin-2-amine as a white solid (5.20 g, 50%). LCMS (ES, m/z): 188,190 [M+H]⁺.

Step 2. (2,6-Dichloro-4-methoxyphenyl)methanol

NaBH₄ (610 mg, 16.1 mmol) was added to a solution of 2,6-dichloro-4-methoxyben- zaldehyde (3.00 g, 14.6 mmol) in EtOH (30.0 mL) at 0 °C. The resulting mixture was stirred for 3 h at 25 °C. The reaction was quenched with NH₄CI (5 mL, sat.) at 0 °C. The resulting mixture was extracted with DCM (3 x 30 mL). The organic layers were combined, washed with brine (50 mL), dried over anhydrous sodium sulfate, filtered and concentrated under vacuum to give (2,6-dichloro-4-methoxyphenyl)methanol as a white solid (2.80 g, crude). GCMS (ES, m/z): 206 [M+H]⁺.

Step 3. 2-(Bromomethyl)-l,3-dichloro-5-methoxybenzene PBr3 (1.46 g, 5.41 mmol) was added to a solution of (2,6-dichloro-4-methoxy- phenyl)methanol (2.80 g, 13.5 mmol) in DCM (30.0 mL) at 0 °C. The resulting mixture was stirred for 1 h at 0 °C. The reaction was quenched with NaHCO₃ (5 mL, sat.) at 0 °C. The resulting mixture was extracted with DCM (3 x 30 mL). The organic layers were combined, washed with brine (30 mL), dried over anhydrous sodium sulfate, filtered and concentrated under vacuum. The residue was purified by silica gel column chromatography (eluting with 1:5 ethyl acetate/petroleum ether) to afford to give 2-(bromomethyl)-l,3-dichloro-5-methoxyben- zene as an off-white solid (3.40 g, 88%). GCMS (ES, m/z): 268 [M+H]⁺.

Step 4. 2-[(2,6-Dichloro-4-methoxyphenyl)methyl]furan

A solution of n-BuLi (3.33 mL, 2.5M in THF) was added to a solution of furan (0.76 g, 11.1 mmol) in THF (30.0 mL) at 0 °C under nitrogen atmosphere. The resulting mixture was stirred for 1 h at 25 °C under nitrogen atmosphere. 2-(bromomethyl)-l,3-dichloro-5-methox- ybenzene (1.50 g, 5.55 mmol) was added. The resulting mixture was stirred for 16 h at 25 °C under nitrogen atmosphere. The reaction was quenched with NH₄CI (sat.) (10 mL) at 25 °C. The resulting mixture was extracted with EA (3 x 30 mL). The organic layers were combined, washed with brine (30 mL), dried over anhydrous sodium sulfate, filtered and concentrated under vacuum. The residue was purified by reverse phase chromatography (Column: C18 silica gel; Mobile phase, A: water (containing 0.05% TFA) and B: ACN (0% to 60% in 30 min); Detector UV 220 nm/ 254 nm) to afford a crude product. It was further purified via Prep-HPLC (Column, Xselect CSH OBD Column, 30 x 150 mm Sum; Mobile phase, A: water (containing 0.05% TFA) and B: ACN (55% to 70% in 8 min); Detector, UV 220/254 nm) to give 2-[(2,6- dichloro-4-methoxyphenyl)methyl]furan as a white solid (200 mg, 13%). GCMS (ES, m/z): 256 [M+H]⁺.

Step 5. 5-[5-[(2,6-Dichloro-4-methoxyphenyl)methyl]furan-2-yl]-N-methylpyrimidin-2- amine

A mixture of 2-[(2,6-dichloro-4-methoxyphenyl)methyl]furan (100 mg, 0.389 mmol), 5-bromo-N-methylpyrimidin-2-amine (109 mg, 0.583 mmol), Pd(OAc)2 (8.73 mg, 0.039 mmol) and KOAc (76.3 mg, 0.778 mmol) in DMA (1.00 mL) was stirred for 48 h at 150 °C under nitrogen atmosphere. The mixture was allowed to cool down to 25 °C and purified by reverse phase chromatography (Column: C18 silica gel; Mobile phase, A: water (containing 0.05% TFA) and B: ACN (0% to 60% in 30 min); Detector: UV 220 nm/ 254 nm) to afford a crude product (20.0 mg). It was further purified via Prep-HPLC (Column, S unfire Prep C18 OBD Column, 19 x 250 mm 10 um; Mobile phase, A: water (containing 0.05% TFA) and B: ACN (60% to 85% in 7 min); Detector, UV 220/254 nm). The collected fraction was lyophi- lized to afford 5-[5-[(2,6-dichloro-4-methoxyphenyl)methyl] furan-2-yl] -N -methylpyrimidin- 2-amine as an off-white solid (5.60 mg, 4%). ¹H-NMR (DMSO-d₆, 400 MHz) δ (ppm): 8.93 (s, 2H), 7.32-7.21 (m, 1H), 7.14 (s, 2H), 6.63 (d, J=3.2 Hz, 1H), 6.05 (d, J=3.2 Hz, 1H), 4.20 (s, 2H), 3.80 (s, 3H), 2.82 (d, J=4.4 Hz, 1H). LCMS (ES, m/z): 364 [M+H]⁺.

Example 3: Synthesis of Compound lb

5-r5-r2.6-dichloro-4-methoxvphenvl)thaiophen-2-vll-N-methvlnvrimidin-2-amine

Chemical Formula: CieHiaCfeNaOS Exact Mass: 365 Molecular Weight: 366

Step 1. 5-Bromo-N-methylpyrimidin-2-amine

A solution of 5 -bromo-2-chloropyrimidine (10.0 g, 51.7 mmol) and a solution of CH₃NH₂ (31.0 mL, 2M in THE) in EtOH (50.0 mL) was refluxed for 16 h at 80 °C under nitrogen atmosphere. The mixture was allowed to cool down to 25 °C. The resulting mixture was concentrated under vacuum. The residue was purified by silica gel column chromatography (eluting with 1:3 ethyl acetate/petroleum ether) to afford 5-bromo-N-methylpyrimidin-2-amine as a white solid (5.20 g, 50%). LCMS (ES, m/z): 188,190 [M+H]⁺.

Step 2. N-methyl-5-(4,4,5,5-tetramethyl-l,3,2-dioxabon>lan-2-yl)pyrimidm-2-amme

A mixture of 5-bromo-N-methylpyrimidin-2-amine (1.00 g, 5.31 mmol), 4,4,5,5-tetra- methyl-2-(tetramethyl-l,3,2-dioxaborolan-2-yl)-l,3,2-dioxaborolane (1.62 g, 6.38 mmol), Pd(dppf)CI₂ CH₂CI₂ (0.430 g, 0.532 mmol) and KOAc (1.57 g, 15.9 mmol) in 1,4-dioxane (10.0 mL) was stirred for 3 h at 80 °C under nitrogen atmosphere. The mixture was allowed to cool down to 20 °C. The reaction was quenched by the addition of water (60 mL). The resulting mixture was extracted with ethyl acetate (3 x 50 mL). The organic layers were combined, washed with brine (50 mL), dried over anhydrous sodium sulfate, filtered and concentrated under vacuum. The residue was purified by silica gel column chromatography (eluting with 1:2 ethyl acetate/petroleum ether) to afford N-methyl-5-(4,4,5,5-tetramethyl-l,3,2-dioxaborolan-2- yl)pyrimidin-2-amine as a yellow oil (1.30 g, 93%). LCMS (ES, m/z): 236 [M+H]⁺.

Step 3. 2-(2,6-Dichloro-4-methoxyphenyl)thiophene

A mixture of 2-bromo-l,3-dichloro-5-methoxybenzene (400 mg, 1.56 mmol), thiophen- 2-ylboronic acid (240 mg, 1.87 mmol), Pd(dppf)CI₂ CH₂CI₂ (255 mg, 0.313 mmol) and K3PO4 (995 mg, 4.68 mmol) in 1,4-dioxane (5.00 mL)/H20 (2.50 mL) was stirred for 5 h at 80 °C under nitrogen atmosphere. The mixture was allowed to cool down to 25 °C. The resulting mixture was diluted with water (20 mL) and extracted with EA (3 x 30 mL). The organic layers were combined, washed with brine (30 mL), dried over anhydrous sodium sulfate, filtered and concentrated under vacuum. The residue was purified by silica gel column chromatography (eluting with 1:2 ethyl acetate/petroleum ether) to afford 2-(2,6-dichloro-4-methoxyphenyl)thi- ophene as a yellow oil (130 mg, 30%). GCMS (ES, m/z): 258 [M+H]⁺.

Step 4. 2-Bromo-5-(2,6-dichloro-4-methoxyphenyl)thiophene

A solution of 2-(2,6-dichloro-4-methoxyphenyl)thiophene (130 mg, 0.502 mmol) and NBS (107 mg, 0.602 mmol) in CCL (2.00 mL) was stirred for 16 h at 60 °C under nitrogen atmosphere without light. The mixture was allowed to cool down to 25 °C and concentrated under vacuum. The residue was purified by silica gel column chromatography (eluting with 1:3 ethyl acetate/petroleum ether) to afford 2-bromo-5-(2,6-dichloro-4-methoxyphenyl)thiophene as a yellow solid (50.0 mg, 28%). GCMS (ES, m/z): 336 [M+H]⁺.

Step 5. 5-[5-(2,6-Dichloro-4-methoxyphenyl)thiophen-2-yl]-N-methylpyrimidin-2-amine

A solution of 2-bromo-5-(2,6-dichloro-4-methoxyphenyl)thiophene (45.0 mg, 0.133 mmol), N-methyl-5-(4,4,5,5-tetramethyl-l,3,2-dioxaborolan-2-yl)pyrimidin-2-amine (37.5 mg, 0.160 mmol), Pd(dppf)CI₂ CH₂CI₂ (21.7 mg, 0.027 mmol) and K3PO4 (84.7 mg, 0.399 mmol) in 1,4-dioxane (1.00 mL) and H₂O (0.50 mL) was stirred for 3 h at 80 °C under nitrogen atmosphere. The reaction mixture was cooled to 25 °C and concentrated under vacuum. The residue was purified by Pre-TLC (eluting with 1 :4 ethyl acetate/petroleum ether) to give a crude product. The crude product was purified via Prep-HPLC (Column, XBridge Shield RP18 OBD Column, 19 x 150 mm 5 um; Mobile phase, A: water (containing 0.05% TFA) and B: ACN (50% to 75% in 8 min); Detector, UV 220/254 nm). The collected fraction was lyophilized to afford 5-[5-(2,6-dichloro-4-methoxyphenyl)thiophen-2-yl]-N-methylpyrimidin-2-amine as an off-white solid (5.10 mg, 10%). 1H-NRR (DMSO-d₆, 400 MHz) δ (ppm): 8.74 (s, 2H), 7.54- 7.39 (m, 2H), 7.23 (s, 2H), 7.09-6.98 (m, 1H), 3.86 (s, 3H), 2.85 (s, 3H). LCMS (ES, m/z): 366 [M+H]⁺

Example 3a: Synthesis of Compound Ic

Chemical Formula: C₁₈H₁₇Cl₃N₄O₃ Exact Mass: 442.04 Molecular Weight: 443.71

Synthesis of Compound 1

To a mixture of 3,5-dichloroanisole (18 g, 97.6 mmol, 1.00 equiv), Paraformaldehyde (4.26 g, 128 mmol, 1.31 equiv) and cone, hydrochloric acid (180 mL) was added cone, sulfuric acid (1.80 mL) at room temperature. After refluxing at 100 °C for 16 hours, the mixture was cooled to room temperature, he resulting mixture was extracted with ethyl acetate (5 x SO mL). The organic layer was dried over anhydrous sodium sulfate, filtered and concentrated under reduced pressure. To the residue were added 1,4-dioxane (100 mL) and a sodium hydroxide aqueous solution (203 mL, 1 M). The mixture was refluxed at 100 °C for 3 hours. The reaction solution was cooled to room temperature, followed by extraction with DCM (5 x SO mL). The organic layer was dried over anhydrous sodium sulfate, filtered and then concentrated under reduced pressure. The residue was purified by silica gel column chromatography (eluting with 85:15 PE/EA) to afford (2,6-dichloro-4-methoxyphenyl)methanol (5.6 g, 26.6%) as a white solid. GCMS (ES, m/z): 206,208.

Synthesis of Compound 2 To a solution of (2,6-dichloro-4-methoxyphenyl)methanol (5.6 g, 26.0 mmol, 1.00 equiv) in DCM (76 mL) was added PBr₃ (2.81 g, 9.97 mmol, 0.40 equiv) at 0 °C. The reac- tion mixture was stirred for 2 h at 0 °C. The reaction was poured into icy water (50 mL). The resulting mixture was extracted with CH₂CI₂ (3 x 50 mL). The combined organic layers were washed with brine (2 x 50 mL), dried over anhydrous Na₂SO₄. After filtration, the filtrate was concentrated under reduced pressure. The residue was purified by silica gel column chroma- tography, eluted with PE/EA (20:1) to afford 2-(bromomethyl)-l,3-dichloro-5-methoxyben- zene (6.9 g, 94.5%) as a white solid. GCMS (ES, m/z): 268, 270, 272.

Synthesis of Compound 3

To a solution of furan (3.50 g, 49.4 mmol, 2.01 equiv) in tetrahydrofuran (35 mL) was added n-BuLi (25 mL, 50 mmol, 2.03 equiv) dropwise at 0 °C. The reaction mixture was stirred for 3 h at room temperature. A solution of 2-(bromomethyl)-l,3-dichloro-5-methoxybenzene (6.9 g, 24.5 mmol, 1.00 equiv) in THF (10 mL) was added dropwise at 0 °C. The mixture was stirred for 1 h room temperature. The reaction was quenched with sat. NH₄CI (aq.) at room temperature. The resulting mixture was extracted with EA (3 x 50 mL). The combined organic layers were washed with brine (2x50 mL), dried over anhydrous Na₂SO₄. After filtration, the filtrate was concentrated under reduced pressure. The residue was purified by silica gel chro- matography (eluting with pure PE) to give 2-[(2,6-dichloro-4-methoxyphenyl)methyl]furan (1.00 g, 15.4%) as a white solid. LCMS (ES, m/z): 257,259 [M+H]⁺.

Synthesis of Compound 4

A solution of 2-[(2,6-dichloro-4-methoxyphenyl)methyl]furan (0.96 g, 3.61 mmol, 1.1 equiv) , bis(pinacolato)diboron (0.85 g, 3.28 mmol, 1.00 equiv) , ( 1 ,5-C YCLOOCTADI- ENE)(METHOXY)IRIDIUM(I) DIMERDi-m-methoxobis( 1 ,5-cyclooctadiene)diiridium (I) (23 mg, 0.033 mmol, 0.01 equiv) and 4,4'-di-tert-butyl-2,2'-bipyridine (26 mg, 0.094 mmol, 0.03 equiv) in hexane (10 mL) was stirred at 80 °C for lh. The mixture was cooled down to room temperature. The mixture was concentrated under reduced pressure. The residue was pu- rified by silica gel chromatography (eluting with 1:1 PE/DCM) to give 2- { 5-[(2,6-dichloro-4- methoxyphenyl)methyl]furan-2-yl } -4,4,5,5 -tetramethyl- 1 ,3 ,2-dioxaborolane (900 mg, 68.0%) as a white solid. LCMS (ES, m/z): 383, 385 [M+H]⁺.

Synthesis of Compound 5 A mixture of 5-bromo-2-iodopyrimidine (400 mg, 1.35 mmol, 1.00 equiv), tert-butyl N- (carbamoylmethyl)carbamate (235 mg, 1.35 mmol, 1 equiv), Pd₂(dba)₃ (123 mg, 0.135 mmol, 0.1 equiv), XantPhos (78 mg, 0.135 mmol, 0.1 equiv), CsF (409 mg, 2.70 mmol, 2 equiv), and dioxane (5 mL) was stirred for 1 h at 80 °C under nitrogen atmosphere. The resulting mixture was cooled down to room temperature, filtered, the filtrate was concentrated under vacuum. The residue was purified directly via reverese phase chromatography (Column: C18 silica gel; Mobile phase, A: water (containing 10 mmoL/L NH₄HCO₃) and B: CH₃CN; Gradient: 0% to 70% in 30 min; Detector 220 nm) to give tert-butyl N-{[(5-bromopyrimidin-2-yl)car- bamoyl] methyl} carbamate (470 mg, 99.0 %) as an off-white solid. LCMS (ES, m/z): 331, 333[M+H]⁺.

Synthesis of Compound 6

A mixture of 2-{5-[(2,6-dichloro-4-methoxyphenyl)methyl]furan-2-yl}-4,4,5,5-tetra- methyl-l,3,2-dioxaborolane (252 mg, 0.624 mmol, 1.10 equiv) , tert-butyl N-{[(5-bromopyrim- idin-2-yl)carbamoyl] methyl} carbamate (163 mg, 0.568 mmol, 1.00 equiv), Pd(PPh₃)₄ (68 mg, 0.057 mmol, 0.1 equiv), NaHCO₃ (120 mg, 1.42 mmol, 2.5 equiv), dioxane (5 mL) and H₂O (1 mL) was stirred for 3 h at 90 °C under nitrogen atmosphere. The resulting mixture was allowed to cooled down to room temperature. The mixture was filtered, the filtrated was purified via reverse phase chromatography (Column: C18 silica gel; Mobile phase, A: water (containing 10 mmoL/L NH₄HCO3) and B: CH₃CN; Gradient: 0% to 70% in 30 min; Detector 220 nm) to give tert-butyl N-{ [(5-{5-[(2,6-dichloro-4-methoxyphenyl)methyl]furan-2-yl}pyrimidin-2- yl)carbamoyl] methyl} carbamate (57 mg, 15.6%) as an off-white solid. LCMS (ES, m/z): 507, 509[M+H]⁺.

Synthesis of Compound 7

To a stirred mixture of tert-butyl N-{ [(5-{5-[(2,6-dichloro-4-methoxyphenyl)methyl]- furan-2-yl}pyrimidin-2-yl)carbamoyl]methyl}carbamate (57 mg, 0.089 mmol, 1.00 equiv) in DCM (5 mL) was added HC1 (gas) in 1,4-dioxane (1 mL, 4M) dropwise at 0 °C . The resulting mixture was stirred for lh at 0 °C under nitrogen atmosphere. The result- ing mixture was concentrated under vacuum. The residue was purified by reverse phase chro- matography(Column, C18 silica gel; Mobile phase, A: water (containing 0.05% HC1) and B: MeCN (30% to 45% in 10 min) to afford 2-amino-N-(5-{5-[(2,6-dichloro-4-methoxy- phenyl)methyl]furan-2-yl}pyrimidin-2-yl)acetamide hydrochloride (19 mg, 46.0%). 1H-NMR (DMSO-d6, 300 MHz) δ (ppm): 11.2 -11.40 (br s, 1H), 8.92 (s, 2H), 8.25 (s, 2H), 7.16 (s, 2H), 7.03(s, 1H), 6.18 (s, 1H), 4.26 (s, 3H), 4.07 (s, 2H), 3.81 (s, 3H). LCMS (ES, m/z): 407,409 [M+H]+.

Example 3b: Synthesis of Compound Id

1

Synthesis of compound 1

A mixture of 5-bromo-2-chloropyrimidine (1 g, 5.12 mmol, 1.00 equiv) and 2-morpho- linoethan- 1 -amine (885 mg, 6.81 mmol, 1.33 equiv) in EtOH (10 mL) was stirred for overnight at 100 °C. The mixture was cooled down to room temperature, concentrated under vacuum. The residue was washed with 20/1 PE/EA to give 5-bromo-N-(2-morpholinoethyl)pyrimidin- 2-amine (1.2 g, 82%) as a white solid. LCMS (ES, m/z): 287, 289 [M+H]⁺.

Synthesis of compound 2 To a mixture of 3,5-dichloroanisole (180 g, 1.02 mol, 1.00 equiv), Paraformaldehyde (40.0 g, 1.33 mol, 1.31 equiv) and cone, hydrochloric acid (1.80 L) was added cone, sulfuric acid (18.0 mL) at room temperature. After refluxing at 100 °C for 16 hours, the mixture was cooled to room temperature. The resulting mixture was extracted with ethyl acetate (5 x 500 mL). The organic layer was dried over anhydrous sodium sulfate, filtered and concentrated under reduced pressure. To the residue were added 1,4-dioxane (1.00 L) and a sodium Hydrox- ide aqueous (2.03 L, 1 M). The mixture was refluxed at 100 °C for 3 hours. The reaction solu- tion was cooled to room temperature, followed by extraction with DCM (5 x 500 mL). The organic layer was dried over anhydrous sodium sulfate, filtered and then concentrated under reduced pressure. The residue was purified by silica gel column chromatography (eluting with 85:15 PE/EA) to afford (2,6-dichloro-4-methoxyphenyl)methanol (56 g, 25.5%) as a white solid. GCMS (ES, m/z): 206, 208.

Synthesis of compound 3

To a solution of (2,6-dichloro-4-methoxyphenyl)methanol (56.0 g, 270 mmol, 1.00 equiv) in DCM (764 mL, 8.99 mol, 44.4 equiv) was added PBr3 (29.3 g, 108 mmol, 0.40 equiv) at 0 °C. The reaction micture was stirred for 2 h at 0 °C. The reaction was poured into icy water (500 mL). The resulting mixture was extracted with CH₂CI₂ (3 x 500 mL). The combined or- ganic layers were washed with brine (2 x 500 mL), dried over anhydrous Na₂SO₄. After filtra- tion, the filtrate was concentrated under reduced pressure. The residue was purified by silica gel column chromatography, eluted with PE/EtOAc (20:1) to afford 2-(bromomethyl)-l,3-di- chloro-5-methoxybenzene (69.5 g, 95.2%) as a white solid. GCMS (ES, m/z): 268, 270, 272.

Synthesis of compound 4

To a solution of furan (35.0 g, 514 mmol, 2.00 equiv) in tetrahydrofuran (350 mL) was added n-BuLi (206 mL, 515 mmol, 2.00 equiv) dropwise at 0 °C. The reaction mixture was stirred for 3 h at room temperature. A solution of 2-(bromomethyl)-1,3-dichloro-5-methox- ybenzene (69.5 g, 257 mmol, 1.00 equiv) in THE (100 mL) was added dropwise at 0 °C. The mixture was stirred for 1 h room temperature. The reaction was quenched with sat. NH₄C1 (aq.) at room temperature. The resulting mixture was extracted with EtOAc (3 x 500 mL). The com- bined organic layers were washed with brine (2x500 mL), dried over anhydrous Na₂SO₄. After filtration, the filtrate was concentrated under reduced pressure. The residue was purified by silica gel chromatography (eluting with pure PE) to give 2-[(2,6-dichloro-4-methoxy- phenyl)methyl]furan (10.4 g, 15.1%) as a white solid. LCMS (ES, m/z): 257, 259 [M+H]⁺.

Synthesis of compound 5

A solution of 2-[(2,6-dichloro-4-methoxyphenyl)methyl]furan (10.4 g, 40.5 mmol, 1.10 equiv), bis(pinacolato)diboron (9.36 g, 36.9 mmol, 1.00 equiv), [Ir(OMe)(COD)]2 (CAS: 12148-71-9) (366 mg, 0.552 mmol, 0.01 equiv), 4,4'-Di-tert-butyl-2,2'-bipyridine (297 mg, 1.11 mmol, 0.03 equiv) and hexane (96 mL) was stirred at 80 °C for 1 h. The mixture was cooled down to room temperature. The mixture was concentrated under reduced pressure. The residue was purified by silica gel chromatography (eluting with 1:1 PE/DCM) to give 2-[5-[(2,6-di- chloro-4-methoxyphenyl)methyl]furan-2-yl]-4,4,5,5-tetramethyl-l,3,2-dioxaborolane (9.5 g, 64.6%) as a white solid. LCMS (ES, m/z): 383, 385 [M+H]⁺.

Synthesis of compound 6

A mixture of 2-{5-[(2,6-dichloro-4-methoxyphenyl)methyl]furan-2-yl}-4,4,5,5-tetra- methyl- 1 ,3 ,2-dioxaborolane (252 mg, 0.624 mmol, 1.10 equiv), 5-bromo-N-(2-morpho- linoethyl)pyrimidin-2-amine (163 mg, 0.568 mmol, 1.00 equiv), Pd(PPh₃)₄ (68 mg, 0.057 mmol, 0.1 equiv), NaHCO₃ (120 mg, 1.42 mmol, 2.5 equiv), dioxane (5 mL) and H₂O (1 mL) was stirred for 3 h at 90 °C under nitrogen atmosphere. The resulting mixture was allowed to cooled down to room temperature. The mixture was filtered, the filtrated was concentrated un- der vacuum. The residue was purified via reverse phase chromatography (Column: C18 silica gel; Mobile phase, A: water (containing 5 mmoL/L HC1) and B: CH₃CN; Gradient: 0% to 50% in 30 min; Detector: 220 nm) to give 5-(5-(2,6-dichloro-4-methoxybenzyl)furan-2-yl)-N-(2- morpholinoethyl)pyrimidin-2-amine hydrochloride (30 mg, 10.2%) as a white solid. LCMS (ES, m/z): 463,465 [M+H]⁺. ¹H-NMR (DMSO-d₆, 400 MHz) δ (ppm): 10.87 (br s, 1H), 8.60 (s, 2H), 7.71 (br s, 1H), 7.14 (s, 2H), 6.71 (s, 1H), 6.08 (s, 1H), 4.20 (s, 2H), 4.04-3.94 (m, 2H), 3.84-3.73 (m, 7H), 3.60-3.49 (m, 2H), 3.33-3.27 (m, 2H), 3.19-3.03 (m, 2H).

Example 4: Biological Testing of Compound la

Control Compound

PF3758309 is an established PAK inhibitor, which is a competitive inhibitor of PAK kinases developed by Pfizer (see Murray et al) and entered into clinical development. PF3758309 is not a selective inhibitor, as it inhibits not only PAKs 1-6, but also off target kinases such as AMPKal, AMPKa2, CDK7, CHK1, CHEK2, MARK3, PKCO, RSK1, RSK2, TSSK1, Yes and Ret (Semenova and Chemoff, 2017), and was eventually withdrawn from clinical trials. The structure of PF3758309 is provided below.

PF3758309

Cell-free kinase assay

In a cell-free kinase assay (Murray B W, Guo C, Piraino J, et al, Proc. Natl. Acad. Sci. USA 2010;107:9446), compound la was found to inhibit PAK4 kinase with IC50 of 0.2-0.5uM, comparable to control compound PF3758309 (see Figure 4). Moreover, compound la did not show significant effect on the kinase activity of PAK1, making it a selective PAK4 inhibitor for cancers such as pancreatic ductal adenocarcinoma (Wang et al, 2018).

Inhibition of different cancer cell-lines

Pancreatic cancer cell lines MiaPaCa-2, PANC1 (human), TB33117 (mouse), and KPCWT833 were used to test the effect of Compound la on cell proliferation. PANC1 and TB33117 cell lines express high levels of PAK1 and PAK4, while MiaPaCa-2 cell has low levels of PAK1 and PAK4 (Yeo, 2014 and unpublished data). Compounds la has been found to inhibit the cell proliferation of PANC1 and TB33117 with IC50 of l.lluM and 1.72 uM respectively, while its effect on MiaPaCa-2 is much weaker (IC50 = 8.29uM). The control compound PF375803 was found to inhibit both PAK1 and PAK4, with IC50 of cell prolifera- tion detected at 0.087uM for MiaPaCa-2, 0.5uM for PANC1 and 0.805uM for TB33117, re- spectively. Compound la was also shown to inhibit colorectal cell line MC-38, brain glioblas- toma cancer cell like U-87, melanoma cell line B16F1, liver cell line HepG2, and bile duct cancer cell line EIG-1 at low to sub-micromolar IC50 values.

IC50 of cell proliferation by Compound la and PF375803 (uM)

Compound la has been shown to be able to inhibit the cell proliferation of pancreatic cancer cells PANC1 and TB33117 at IC50 of 1.0-2.0 uM. Compound la has also been shown to inhibit the proliferation of colon cancer cells, brain tumour cells, skin cancer cells, liver cancer cells, and cholangiocarcinoma cells.

Example 5: Effects of Compound la on PD-L1 Expression

Cells from a colorectal cancer cell line (DLD-1) were incubated with Compound la (0, 1, 10, 20, 50 μΜ), or with compound PF-3758309 (500 nM) for 24 h. At the end of 24 h culture, the medium was removed from the cells, and the cells were washed once with PBS. The cells were lysed in SDS-sample buffer. The resultant cell lysates were subjected to 10% SDS-PAGE to separate the proteins with different molecular weights, which then were blotted with anti- bodies against PD-L1, PAK1, PAK4, α-SMA and GAPDH.

Compound la was shown to dose-dependently inhibit the expression of PD-L1 in the colorectal cancer cell line DLD-1. This was associated with a reduced expression of PAK4 and alpha smooth muscle actin (α-SMA). Compound la reduced the expression of PD-L1 to a comparable level of PD-L1 when inhibited by PF-3758309, a pan-PAK inhibitor.

The inhibitory effect of Compound la on the expression of PD-L1 in cancer cells is expected to decrease the binding of PD-L1 to PD-1 on the surface of T cells, and therefore facilitate the effect of immune checkpoint inhibitors. Example 5a: Effects of Compound la on CHEK2 inhibition

The effects of Compound la on CHEK2 kinase activity was assessed using an ADP-Glo kinase assay kit purchased from Promega (Sydney, NSW, Australia). The assay was undertaken in accordance with the manufacturer’s instructions.

The results, shown in Figure 6, demonstrate that Compound la is able to inhibit CHEK2 with an IC50 value of 737 nM.

Example 6: Efficacy of Compound la in Combination with Gemcitabine

The in vivo efficacy of Compound la in combination with anticancer agent, Gemcita- bine, was assessed.

Male C57B16 (6-week-old) were subcutaneously injected KPC833 cells (50,000 cells/100 ul) at the back of a hind leg. When tumour volume reached 50 or 100 mm³, PAK227 (40 mg/Kg) was given by subcutaneous injection every other day, and gemcitabine 25 or 50 mg/Kg) was given by intraperitoneal injection every 4 days for 3 weeks or more. Tumour vol- ume was measured using a calliper. Tumour weight was measured at the end of experiments.

The results, shown in Figure 7, demonstrate that combination treatment of Compound la and Gemcitabine, for a duration of both 21 days (Figure 7a) and 31 days (Figure 7b), caused regression of pancreatic tumour growth as evidenced by a decrease in tumour volume compared to untreated control tumours. Beneficially, this tumour regression was observed without in- creased toxicity (e.g., no body weight loss was observed).

The combination treatment of Compound la and Gemcitabine also demonstrated im- proved efficacy compared to Gemcitabine treatment alone, when tested against advanced tu- mours (size = 100 mm³), as shown in Figure 7c.

Intra-tumour injection of Compound la at 10 mg/kg on day 1, followed by gemcitabine treatment (50 mg/kg) also demonstrated efficacy as observed by decreased tumour volume over 21 days compared to gemcitabine treatment alone, as shown in Figure 7d. From this, it can be concluded that a single dose injection of Compound la significantly enhances the anti-cancer effect of Gemcitabine.

Example 7: Effects of Compound la on Immunological Biomarkers

The effects of Compound la on immunological biomarkers was assessed using synge- neic mouse models of pancreatic cancer. Single cell suspension was made from tumour tissues isolated from mice treated with either gemcitabine alone or gemcitabine plus PAK227. The cell suspension was incubated with antibodies against CD45, CD4, CDS, B220, PD-L1, PD-1, CD1 lb and Ly6c, and then subjected to a flow-cytometry machine for cell number counting and percentage calculation.

The results, shown in Figure 8, demonstrate that Compound la in combination with Gemcitabine increases the expression of immunological biomarkers in tumour tissues in com- parison to Gemcitabine treatment alone.

Example 8: Prodrug Formulation of Compound la

The efficacy of a prodrug formulation of Compound la was assessed. The prodrug, Compound Ic, was synthesised and characterised according to Example 3a.

Pancreatic cancer cells (BxPC) were seeded at 5000 cell/lOOul/well in a 96-well plate overnight. The cells were then treated with Compound Ic with concentrations indicated in the figure in the absence of serum for 24 hours. By the end of 24 hour incubation, MTT assay was performed to measure the cell proliferation. The values obtained in control (non-treated) cells were taken as 100%.

The prodrug derivative, Compound Ic, of Compound I is able to be dissolved in a 67% ethanol in water solution, suitable for intraperitoneal, intravenous, and subcutaneous admin- istration. Further, the results, shown in Figure 9, demonstrate that the prodrug, Compound Ic, of Compound la is able to inhibit pancreatic cell proliferation with similar potency to Com- pound la.

References

Amro Aboukameel, A. Irfana Muqbil, William Senapedis, Erkan Baloglu, Yosef Landesman, Sharon Shacham, Michael Kauffman, Philip A. Philip, Ramzi M. Mohammad, and Asfar S. Azmi, Mol. Cancer Ther., 2017, 16(1), 76-87.

Dart AE, Wells CM, Eur J. Cell Biol. 2013: 92:129.

Hakoshima T, Shimizu T, Maesaki R, J. Biochem. 2003; 134:327.

Kimmelman AC, Hezel AF, Aguirre AJ, et al, Proc. Natl. Acad. Sci. USA, 2008; 105:19372. Mehlamaki EH, Kauraniemi P, Monni O et al, Neoplasia, 2004;6:432.

Murray B W, Guo C, Piraino J, et al, Proc. Natl. Acad. Sci. USA 2010;107:9446.

Ndubaku, C.O., Crawford, J.J., Drobnick, J., Aliagas, L, Campbell, D., Dong, P., Doman, L.M., Duron, S., Epler, J., Gazzard, L., Heise, C.E., Hoeflich, K.P., Jakubiak, D., La, H., Lee, W., Lin, B., Lyssikatos, J.P., Maksimoska, J., Marmorstein, R., Murray, L.J., O'Brien, T., Oh, A., Ramaswamy, S., Wang, W., Zhao, X., Zhong, Y., Blackwood, E., Rudolph, J. Acs Med.Chem.Lett. 2015; 6: 1241-1246.

Rudolph, J., Crawford, J.J., Hoeflich, K.P., Wang, W., J. Med. Chem. 2015; 58: 11-129 Semenova G, Chemoff J. Biochem. Soc. Trans. 2017;45:79.

Wang, K., Huynh, N., Wang, X., Baldwin, G., Nikfaijam, M., He, H., Int. J. Oncol. 2018; 52:261-269

Yeo D, Huynh N, Beutler J A, et al, Cancer Lett, 2014;346:264.

Zhang, E.Y., Ha, B.H., Boggon, T.J. (2018) Biochim. Biophys. Acta 1866: 356-365.

Staben, S.T., Feng, J.A., Lyle, K., Belvin, M., Boggs, J., Burch, J.D., Chua, C.C., Cui, H., Di- pasquale, A.G., Friedman, L.S., Heise, C., Koeppen, H., Kotey, A., Mintzer, R., Oh, A., Ro- berts, D.A., Rouge, L., Rudolph, J., Tam, C., Wang, W., Xiao, Y., Young, A., Zhang, Y., Hoe- flich, K.P. J.Med.Chem. 2014; 57: 1033-1045.

Claims

1. A compound of Formula (I) or a salt thereof:

X is S, O, or NH;

R⁶ is selected from the group consisting of hydrogen, halogen, C_1-4alkyl, -O-C_1-4alkyl, C_1-4haloalkyl and -O-C_1-4haloalkyl;

R⁷ is selected from the group consisting of hydrogen, halogen, -CN, -C_1-6alkyl, C_{3 -10}carbocy- clyl, C_3-10heterocyclyl, -O-C_1-6alkyl, -O-C_3-10carbocyclyl, -O-(3-10 membered heterocyclyl), - NH(C_1-6alkyl), -N(C_1-6alkyl)₂, -NH-C_3-10carbocyclyl, -N(C_1-4alkyl)-C_6-10carbocyclyl, -NH-(3- 10 membered heterocyclyl), -N(C_1-4alkyl)-(3-10 membered heterocyclyl), -C(O)-C_1-4alkyl, - C(O)-C_3-10carbocyclyl, -C(O)-(3-10 membered heterocyclyl), and -C(O)N(C_1-4alkyl)₂, wherein said alkyl, carbocyclyl or heterocyclyl may be unsubstituted or substituted with up to two substituents each independently selected from the group consisting of C_1- ₄alkyl, oxo, halogen and C_1-4haloalkyl;

R⁹ is selected from the group consisting of hydrogen and halogen;

2. The compound or salt as claimed in claim 1 , wherein R¹ and R⁵ are each independently selected from the group consisting of halogen and C_1-4alkyl.

3. The compound or salt as claimed in claim 1 or 2, wherein R¹ and R⁵ are each halogen.

4. The compound or salt as claimed in claim 3, wherein R¹ and R⁵ are each chlorine.

5. The compound or salt as claimed in any of claims 1 to 4, wherein R³ is selected from the group consisting of C_1-6alkyl, -O-C_1-6alkyl, phenyl, or 5-6 membered heteroaromatic, said phenyl or heteroaromatic being unsubstituted or substituted by one or two C_1-4 alkyl groups.

6. The compound or salt as claimed in claim 5, wherein R³ is -O-C_1-4alkyl.

7. The compound or salt as claimed in claim 6, wherein R³ is -O-CH₃.

8. The compound or salt as claimed in any of claims 1 to 7, wherein R² and R⁴ are each hydrogen.

9. The compound or salt as claimed in any of claims 1 to 8, wherein R⁶ is selected from the group consisting of hydrogen, halogen, C_1-4alkyl and -O-C_1-4alkyl.

10. The compound or salt as claimed in claim 9, wherein R⁶ is hydrogen.

11. The compound or salt as claimed in any of claims 1 to 10, wherein R⁷ is selected from the group consisting of hydrogen, -C_1-6alkyl, C_3-10carbocyclyl, -O-C_3-10carbocyclyl, -NH-C₃- ₁₀carbocyclyl, C_3-10heterocyclyl, -O-C_3-10heterocyclyl and -NH-C_3-10heterocyclyl.

12. The compound or salt as claimed in claim 11, wherein R⁷ is hydrogen.

13. The compound or salt as claimed in any of claims 1 to 12, wherein R⁸ is selected from the group consisting of hydrogen, -C_1-4alkylene-R¹³, -O-C_1-4alkylene-R¹³ and -O-R¹³, and R¹³ is selected from the group consisting of hydrogen, -C_1-6alkyl, C_3-10carbocyclyl, -O-C_3-10carbo- cyclyl, -NH-C_3-10carbocyclyl, C_3-10heterocyclyl, -O- C_3-10heterocyclyl and -NH-C_3-10heterocy- clyl.

14. The compound or salt as claimed in claim 13, wherein R⁸ is hydrogen.

15. The compound or salt as claimed in any of claims 1 to 14, wherein R⁹ is hydrogen.

16. The compound or salt as claimed in claim 15, wherein R⁸ and R⁹ are each hydrogen.

17. The compound or salt as claimed in any of claims 1 to 16, wherein R¹⁰ is selected from the group consisting of hydrogen, C_1-6alkyl, C_1-6haloalkyl, C_6-10aryl, -R¹⁴, -C_1-6alkylene-R¹⁴ and -C_6-10arylene-R¹⁴, wherein said aryl or arylene may optionally be substituted with one or two substituents each independently selected from the group consisting of C_1-4alkyl, halogen and C_1-4haloalkyl.

18. The compound or salt as claimed in claim 17, wherein R¹⁰ is -CH₃.

19. The compound or salt as claimed in any of claims 1 to 18, wherein n is 1.

20. The compound or salt as claimed in any of claims 1 to 19, wherein X is O.

21. The compound or salt as claimed in claim 19 or 20, wherein n is 1 and X is O.

22. The compound or salt as claimed in claim 21, wherein R¹ and R⁵ are chlorine, R³ is - OCH₃, and R² and R⁴ are each hydrogen.

23. The compound or salt as claimed in claim 22, wherein the compound of Formula (I) is

(Ia).

24. The compound or salt as claimed in any of claims 1 to 22, wherein the compound of

Formula (I) is

(Ic).

25. The compound or salt as claimed in any of claims 1 to 22, wherein the compound of

Formula (I) is

(Id).

26. The compound or salt as claimed in any of claims 1 to 18, wherein n is 0.

27. The compound or salt as claimed in any of claims 1 to 18 or 26, wherein X is S.

28. The compound or salt as claimed in claim 26 or 27, wherein n is 0 and X is S.

29. The compound or salt as claimed in any claim 28, wherein R¹ and R⁵ are chlorine, R³ is -OCH₃, and R² and R⁴ are each hydrogen.

30. The compound or salt as claimed in claim 28, wherein the compound of Formula (I) is

(lb).

31. A pharmaceutical composition comprising the compound or salt as claimed in any of claims 1 to 30, and a pharmaceutically acceptable excipient.

32. A pharmaceutical composition as claimed in claim 31, further comprising a further therapeutic agent.

33. A pharmaceutical composition as claimed in claim 32, wherein the further therapeutic agent is an anti-cancer agent.

34. A pharmaceutical composition as claimed in claim 32 or claim 33, wherein the further therapeutic agent is selected from the group consisting of ipilimumab, bevacizumab, pemetrexed, platinum chemotherapeutics, a taxane, etoposide, and gemcitabine.

35. A pharmaceutical composition as claimed in any of claims 31 to 34, further comprising a checkpoint inhibitor.

36. A pharmaceutical composition as claimed in any of claims 31 to 35, wherein the check- point inhibitor is a PD-1 or PD-L1 inhibitor.

37. A pharmaceutical composition as claimed in any of claims 31 to 36, wherein the check- point inhibitor is selected from the group consisting of nivolumab, pembrolizumab, pidili- zumab, AMP-224, TSR-042, BMS-936559, BMS-1001, BMS-1166, BGB-A317, atezoli- zumab, avelumab, cemiplimab, and durvalumab.

38. A pharmaceutical composition as claimed in any of claims 31 to 35, wherein the check- point inhibitor is a CHEK2 inhibitor.

39. A pharmaceutical composition as claimed in any of claims 31 to 35 and 38, wherein the checkpoint inhibitor is selected from the group consisting of CCT241533 and BML-277.

40. A compound or salt as claimed in any of claims 1 to 30, or a pharmaceutical compo- sition as claimed in any of claims 31 to 39, for use in therapy.

41. A compound or salt as claimed in any of claims 1 to 30, or a pharmaceutical compo- sition as claimed in any of claims 31 to 39, for use in immunotherapy.

42. A compound or salt as claimed in any of claims 1 to 30, or a pharmaceutical compo- sition as claimed in claim any of claims 31 to 39, for use in preventing or treating cancer.

43. A method of reducing PD-L1 expression, comprising contacting a compound or salt as claimed in any of claims 1 to 30, or a pharmaceutical composition as claimed in any of claims 31 to 37, with a PAK enzyme.

44. A method of decreasing the binding of PD-L1 to PD-1, comprising contacting a com- pound or salt as claimed in any of claims 1 to 30, or a pharmaceutical composition as claimed in any of claims 31 to 37, with a PAK enzyme.

45. A method of decreasing CHEK2 expression, comprising contacting a compound or salt as claimed in any of claims 1 to 30, or a pharmaceutical composition as claimed in any of claims 31 to 36, 38, and 39, with a PAK enzyme.

46. A method of inhibiting CHEK2, comprising contacting a compound or salt as claimed in any of claims 1 to 30, or a pharmaceutical composition as claimed in any of claims 31 to 36, 38, and 39, with a PAK enzyme.

47. A method of preventing or treating cancer in a subject, comprising administering an effective amount of the compound or salt as claimed in any of claims 1 to 30, or a pharmaceu- tical composition as claimed in any of claims 31 to 39, to the subject.

48. A method of immunotherapy, comprising administering an effective amount of the compound or salt as claimed in any of claims 1 to 30, or a pharmaceutical composition as claimed in any of claims 31 to 39, to the subject.

49. Use of a compound or salt as claimed in any of claims 1 to 30, in the preparation of a medicament for use in immunotherapy.

50. Use of a compound or salt as claimed in any of claims 1 to 30, in the preparation of a medicament for use in preventing or treating cancer.

51. The compound or salt as claimed in any of claims 40 to 42, the method as claimed in any of claims 43 to 48, or the use as claimed in claim 49 or claim 50, wherein the compound or salt, or pharmaceutical composition, is administered in combination with a further therapeutic agent.

52. The compound or salt, method, or use, as claimed in claim 51, wherein the further therapeutic agent is an anti-cancer agent.

53. The compound or salt, method, or use, as claimed in claim 51 or claim 52, wherein the further therapeutic agent is selected from the group consisting of ipilimumab, bevacizumab, pemetrexed, platinum chemotherapeutics, a taxane, etoposide, and gemcitabine.

54. The compound or salt, method, or use, as claimed in any of claims 51 to 53, wherein the compound or salt, or pharmaceutical composition, further comprises a checkpoint inhibitor.

55. The compound or salt, method, or use, as claimed in any of claims 51 to 54, wherein the checkpoint inhibitor is a PD-1 or PDL-1 inhibitor.

56. The compound or salt, method, or use, as claimed in any of claims 51 to 55, wherein the checkpoint inhibitor is selected from the group consisting of nivolumab, pembrolizumab, pidilizumab, AMP-224, TSR-042, BMS-936559, BMS-1001, BMS-1166, BGB-A317, atezoli- zumab, avelumab, cemiplimab, and durvalumab.

57. The compound or salt, method, or use, as claimed in any of claims 51 to 54, wherein the checkpoint inhibitor is a CHEK2 inhibitor.

58. The compound or salt, method, or use, as claimed in any of claims 51 to 54 and 57, wherein the checkpoint inhibitor is selected from the group consisting of CCT241533 and BML-277.

59. The compound or salt, method, or use, as claimed in any of claims 51 to 58, wherein the cancer is selected from the group consisting of melanoma, kidney cancer, bladder cancer, head and neck cancer, Hodgkin’s lymphoma, pancreatic cancer, breast cancer, gastric cancer, glioma, hepatocellular cancer, cholangiocarcinoma, lung cancer, ovarian cancer, osteosarcoma, oesophageal squamous cell cancer, colon cancer, prostate cancer, colorectal cancer, brain glio- blastoma, liver cancer, and bile duct cancer.

60. The compound or salt, method, or use, as claimed in any of claims 51 to 59, wherein the cancer is selected from the group consisting of melanoma, kidney cancer, bladder cancer, head and neck cancer, Hodgkin’s lymphoma, and lung cancer.

61. The compound or salt, method, or use, as claimed in any of claims 51 to 59, wherein the cancer is selected from the group consisting of pancreatic cancer, breast cancer, gastric cancer, glioma, hepatocellular cancer, cholangiocarcinoma, lung cancer, ovarian cancer, oste- osarcoma, oesophageal squamous cell cancer, colon cancer, and prostate cancer.